Effect on getting a new visa

I've been doing Kitchen part-time jobs in chain tens ever since I got here in Japan coz it's the easiest part-time to find. I'm now on my second year of language school and I switched part time 4 times already coz it didn't fit me. (I never work beyond the 28hr/wk rule) I took the part-time job because sometimes there are no other options and I needed money for a bit of allowance. Now, I know my Japanese gotten better and would like to change again a part-time job. My questions is, will it affect my visa renewal or whenever I got a job here in Japan due to changing multiple part-time jobs?

As long as you maintain your good attendance (>80%) at school, obtained good results and can show enough financial support(pay school fees), not problem with school, then you should be OK with renewal.
Changing multiple ptime jobs won't matter much, as long as you keep your working hours under 28hrs/week and not affecting your study.