Where did I go wrong?

My game at this stage is filled with bugs which I am still uncertain how to fix. Some things worked out ok but often as a result of what I really wanted failing. For example where the dialogue box appears upon collision, I had wanted it to appear after pressing a key, however I was unable to find a way to make that work in my script, perhaps due to outdated tutorials, or I should have worked in an older version. I also faced a glaring issue I still have not found a fix for, which is my character is unable to jump without jumping for eternity. This was not always the case, but I was unable to pinpoint what I must have changed for this to be possible. I did manage to learn a lot during the process of this game, as this is my first experience with Unity, I found it was very rewarding when you managed to get something to work the way you were hoping, as I felt when I had initially made the dialogue box work exactly how I wanted with text coming up letter by letter, and then it was interesting to see how even when I thought something worked on its own, I couldn't get it to work with the rest of the mechanics. I wish I had a lot more time to dedicate solely to learning more about Unity, but unfourtunately with other projects being ongoing, there is still a lot I have left to learn. There is a lot that can be thoroughly improved upon, even something like the terrain ended up looking awfully boring as the terrain and low poly assets did not go together so I ended up removing the majority of the environment in favour of having less error codes.