I am currently a specialist at Codeforces, and I have been practicing for about 1 year. I am able to solve most problems up to 1600 rating, but I am struggling to reach expert rating.

I have the following questions:
1. What is the best strategy to follow to reach expert rating at Codeforces?
2. How many questions should I do and in how much time in DIV2 and DIV3 contest?
3. What rating questions should I practice?(Please share some quality questions or websites or problem links)
4. Is it okay to practice 1800 and 1900 rated questions, even if I am not able to solve most of them?
5. How much time should I spend on a problem before I give up and look at the editorial?
6. Should I leave a problem and try it again on another day if I am not able to solve it?
7. Sometimes I am able to solve problems after the contest(easily) that I was not able to solve during the contest. How can overcome this problem?
I would appreciate any advice that you can give me.
Thanks :)