Some advice to help put the phone down.

Delete all social media apps. They are built to be addictive. If you can't have a healthy relationship with them, delete them and maybe a week or month later reevaluate if you need them.

Put your phone in greyscale or black/white mode. This one will sound odd, but your brain is so much less interested in constantly being on the phone in grey mode. Plus it's a visual reminder to not be on the phone too much.

As for apps to help, I do not have any good apps for productivity. I just use goodreads to keep track of what I am reading and what I plan on reading. I try to write a review of everything I read just to help others, but don't go overboard into the social aspect of the app.