Rather than tell you to RTFM I’ll direct you to this post that seems to be constructively talking about the topic. Text Mesh Pro Dozens of errors with Unity 2019.1
FYI: You’re not the only one getting snagged on this issue. I just hit this bug today too. I was once a newbie as well so I understand how frustrating this can be to not know exactly where to find answers after putting some time into trying to fix an issue that’s not really your fault. It’s best to try and remain persistent as it’s the nature of the work. Don’t worry, this is normal, and despite the attitude that some folks have in regards to someone else asking the questions, not everyone feels the same. Luckily there are people out there who will un-begrudgingly try to help you find the answer.
It’s never a dull day being a developer just trying to do the thing you actually set out to do that day and not the over 9000 other things that you end up needing to fix before you can get started.
Anyway… Good luck. Have fun! 