What’s wrong with my MacBook Pro

I know y’all are busy but my question is more troubleshooting. I need some information on what happened.

I have a 2011 15” MacBook Pro, I recently replaced my whole display screen. I also have not used the computer for 2 years. I’m a graphics designer so I know that’s also important to know software wise.

The replacement went totally fine, but It shows 2 distorted grey screens with the Apple and everything then loads a colorful screens then eventually it shows which account to sign in screen. So it works. I tried the internet and it works and updated my Microsoft Word suite and that worked too. Why is it having a hard time with the loading screens process and why is that?

I tried to start up Adobe Illustrator and the system shut down on its own, I managed to load the newest operating system for my system which is still not newest but needed to do a restart to do so, but don’t think it worked and because it loads a disorder grey screen, does nothing  and then a solid grey screen and more nothing?

What can I do? Is it the battery? Is it the logic board?

The computer turns on only when the power port is plugged in but it doesn’t charge the battery, stays on green. Before the attempt on getting a new operating system it would say 0% or 1 %. I will replace the battery.

Any thoughts, any ideas I’m all ears. Please let me know. I’m new with this computer stuff (hardware) but it would really cool to rebuild my computer and start my graphic designing again.

Thank you have a great and safe day