Yes, if you read aloud rhyming phrases, or practice reading or singing song lyrics, you can improve your pronunciation. Watching a movie repeatedly, and repeating the dialogue can be a benefit.

I think yes, if you already have good examples to follow and you're honest with yourself about how you sound. If there's no-one else to talk to, of course you can talk to yourself. :) On the other hand, it is possible to just guess at pronunciation or grammar, and talking to yourself would mean repeating errors. As long as you get some honest feedback, even if it's from yourself, this shouldn't be a problem.

i thinks this video can help u, https://www.youtube.com/watch?v=QRPW_awvlCg