You won't memorize the entire method of how to do something on just one walkthrough with a tutorial anyway, so it's normal to have forgotten stuff.
Instead of immediately jumping for a tutorial, try at least coming up with an idea on your own. Programming isn't so much typing code and memorizing languages and engines as it is problem solving and creating solutions. The language and engine are just tools that assist you with that. But the actual solutions you come up with in your head are the real 'program'
It may seem intimidating, but it's good to fail. You can't get better without failing first. Just try to come up with the idea, and then use the Unity manuals and documentation to try to find a way to do it. Until you get really used to Unity and have a lot of experience with it, you might not really know where to look, so it will be really hard at first.
If you think you've found something that works, go ahead and put it in your project! If you can't come up with a solution, or you think yours is really messy and probably shouldn't go into your game, try looking up a tutorial. Also, think of tutorials more like examples rather than actual lessons on how to do things. What you should be taking from them is the general concepts. You can apply them to all kinds of situations!
And, don't feel bad that you have to look something up. Even the most experienced programmers still look up stuff in the documentation for languages and engines. The more you do it, the more you'll memorize, but no one expects you to memorize every sing keyword and function and monobehavior and etc. It's normal to have to look it up. So if your problem is that you don't remember the exact thing you're supposed to type, that's completely normal and not even a beginners' thing. A lot of people keep a reference list of the stuff they need to remember the most. Especially when you jump between languages with pretty different syntax, it's nice to know stuff like... how a for loop works or something. So just have a little notebook with the most common stuff like that, or whatever.
And you will need tons and tons of practice before you just come up with solutions with ease. In the beginning, you're going to have to think about it a lot, and will probably come up with plenty of crummy solutions along the way. It's totally fine!!
I guess what I'm saying is don't feel bad or feel like you're failing. You're right on track and you're doing exactly how you should. The best way to grow is to challenge yourself, so instead of immediately falling to a tutorial, try your own solution first, then go to the tutorial. This is normal! Even pro devs talk about their solutions with each other to get new ideas (that kind of thing is why forums like this exist!) so it's normally to learn from other people, whether it's a tutorial or whatever.