removing accounts

No need to do that. Try to manage your credit cards in a proper way. Make bill payments within the stipulated time. And don't cross your credit limit. If you remain consistent with it, your credit score will improve.

You can surely fix errors in your credit report yourself. Just monitor your credit reports at regular intervals and dispute errors if any. Along with that, add positive items in your reports.

You can't remove accurate negative listings from your credit report. Always, remember that. They will stay on your credit report for 7 years. You can only request to remove wrong negative listing from your credit report.

You can use this sample letter.
https://community.debtcc.com/letters/sample13.html

Check for errors, monitor your credit reports at regular intervals. These little errors sometimes may cost you more. Don't forget to pay your bills before due date and try to keep your credit balances less that 30% of your credit limit.