Like others have said, you want it to just work. Albeit that is an understandable sentiment, you as well as all of us know that computers in general are not like that, specially when trying to make a fairly complex piece of software work from the ground up and if you do not know even the basics. There is always a learning curve and it is not reasonable to assume that it will work like magic.
If you are a newcomer with Linux or command line you will have that learning curve, no different if you were utterly new to Windows or computers in general. On top that there is a difference between being an end user and what you are trying to do, which is to assume a bit of an Administrator role, on top of being an end user.
I get your frustration, yet if you are newbie to the whole environment, it is no different than learning a new instrument. You cannot expect to just be given a violin and then start just playing a piece without issues.
Like others have said, you may need to start learning and playing around with the environment more. I got a coupon for a free VPS for like a month and I just played around and broke it numerous time so I learn what to do and what NOT to do in many situations. Like you I started as a newbie, being afraid of messing stuff up because I did not know or understood what I was doing and I certainly broke my install a number of times but with that came more expertise.
I am no one special in this context, we all go through that and certainly I am no engineer of any sort.
For what I can tell it seems you are using a bit of a throw stuff at the wall and see what sticks and hope that it somehow works. That will just leave you frustrated in the end. It would leave anyone frustrated.
Perhaps take a step back and remove the expectation that doing a few click is all you need. You have to understand the lay of the land before you start deploying software and think that it will just work, or at the very least that is the best approach long term. Not trying to come off as mean, but at the very least if you have no idea of what the Stack is, and do not want to learn then yeah, maybe just quit. It is up to you. But if you want to have it work, whether is Nextcloud or any other complex piece of kit, then you have to go through those growing pains of the learning curve. This applies to any skill.
Like others have said, once you know the basics, it is not only worth it, it totally is, but you only have to learn things once. We all have gone through the same.
You can only get out what you put it, but you have to do it in a way that you are actually learning and it does take time, there are no shortcuts there.