What should be a game developers main focus while developing? And what are the best developing softwares, please help I'm fairly few at developing.

You might not want to hear that, but the first thing is planning. Make a list of features, you want to incorporate into your game. Make sure, you thought everything through at least once.

Of course, things may change over the course of this living process and new features may be added during that. But the more you are prepared the better. The trap of "oh no, I forgot that one feature, now I got to rebuild the whole thing again" is lurking everywhere.

My advice, if you're new to it, is make lots of games. Make them fast and learn as much as you can from it every time. If you're goal is to improve as a game designer, share them with players and watch them play; get their feedback.

Doing game jams or maintaining the discipline for: http://www.onegameamonth.com/ might be a good way to start.

Regarding software, it's really about what feels best for you. Some popular options include Unity3D, Gamemaker, Construct 2, Unreal.

I hope that helps, good luck!

Pen and paper is the first step.

Get an idea, break it down.  Think about what engine you're going to make and then list all the variables you'll use, input, et cetera.  Then plan on making each of those modules one at a time.

Example: Flappy bird.  Bird graphic, Pipe graphic, one button input, collision.  Variables : score, maybe x/y co-ordinates depeninding on what engine/how you're scripting it. 

Then I'd get the graphic of the bird, write the input script, write the collission script.

Plan , Plan , Plan

Once you done that you can move on to realising that.

1.Codes/Skripts

2. Marketing (Yes this is really important , no one is going to play if they dont know that game exist)

3.Graphics

4.Sound

5.If you on a roll you can expand your game, make a little things, consumers noticing that.

6.Publishing

I advice to start marketing campaign when you alredy have something to show.

As with others, planning is always first, followed by prototyping.

As you're in for beginners, you're probably not talking about a commercial game, instead you're looking for learning experiments.

Figure out the thing you want to learn, and make a game that implements those things you want to learn. Implement it and learn the things. Experiment with it so you know you've learned it.  Once you've learned what you need, go back and look for another learning experiment.

However, if you are thinking about a commercial product there is much more planning.

What type of game are you going to make? Are you experienced enough to create it? Are you operating professional enough that you are not just able to create it, but also put it on a marketplace? If so, who is your target player, how many would likely buy the game, how much would your investment pay off, and how would you market the game and get it into the hands of players?  What help will you need to hire? How will you ensure you are complying with laws like business incorporation, business laws, taxes, and if you hire or contract with someone, how will you verify you've got proper contracts to ensure the proper rights are transferred to the company, ensure employment laws or contracting laws to ensure you report wages and taxes and other governmental concerns correctly?

Once you know what you are making it and why you are making it and that you are following all the business laws, you'll be able to plan what is in it and how to create it.  You need to assess if you are able to create them, or if you need more information about what they are, or if you need more practice at creating whatever they are. Figure out how to close all those gaps.

Then you'll go back to the first steps and revisit them all.  Are you sure you have the needed experience to create that game? Will you need to hire help to create it? Are you doubly-sure there is a market?

Once you have all that, make paper prototypes to ensure it is actually fun and actually does what you think it will do.  That can mean actual paper cutouts, notes carefully made on notebooks and/or spreadsheets, and whatever else is needed to test out the concepts. Play it with others to make sure you have recorded all the things you actually need, since usually pieces are missing.

Then go back to the first steps and revisit them all again. Are you still sure you have the experience to create the game you're planning? Will you need help? Are you triply sure there is a market and you'll be able to recover the investments? Do you understand how you will market and distribute it?

Now that you've got your plan for your game and you understand the mechanics of the game, and you're sure that since it is a commercially-intended project you can make it commercially viable, you've got the details to you start to execute your plan with a prototype.  You build a prototype with the key mechanics to make sure they work out. Usually this means using an engine to build worlds filled with boring boxes and other simple geometry, and only enough game code to experiment 

Then you repeat the earlier steps, make sure you can do all the things, completely discard the prototype, and start making the game for real.  Work on it for many months doing all the typical development, and in the end you build a game. Execute your marketing and distribution plans.  Iterate on the project, on the marketing, and the distribution, until you start making money. That may take many iterations, maybe five or ten or fifty, depending on how well you understand the details and how well you planned for the target market.

Not really something to "focus" on, but definitely something to keep in mind is a monetization strategy.  Sometimes, forgetting this step can be troublesome when going back.

Good luck!

These are excellent advises and information thank you guys

Planning your project is always an important thing. I use Google Keep to store a lot of my notes when I plan my projects. Also, you need to have the right attitude and make sure you finish your project. Being able to say that you finished something is a serious accomplishment when just starting out!