I need some advice for mma training?

My two cents...

You should probably do a lot of different types of exercises, hopefully that correspond to working out the muscles you would use in a fight based on your style. Sit ups would be one of many different exercises you should do. There are also a few different variants to the traditional sit up that might be more suited to MMA... have you seen the Rushfit workout videos by GSP?

I'd say you should run as it is pretty useful. If you want to be a fighter, why not 5, 5 minute rounds of hard running with 2 minute of jogging between each round.