The monthly income is 2 100, and the rent is 700. I want to manage the rest of the money. How to manage? How about lump-sum deposit and withdrawal, and how about fixed investment of the fund?

Nobody said you wanted to advertise, so you were there for no reason, haha. I also suggest that you save some money in lump sum. If you want to buy a fund, you can buy a fixed investment, which is similar to saving money, but stock funds are suitable for people with more money to get rich, and people with less money can at most seek a capital preservation or not to depreciate.

If you have knowledge, you really should do some research and try to find a better job and raise your salary. If you have a family and social background, you can take an examination of village officials and civil servants (although I don't like these). Where there are benefits, there are great prospects. If you are just an ordinary ant family and have no special business sense (I don't mean to look down on people, I belong to this kind of person), then work hard step by step, reduce job-hopping, save money regularly (funds are also acceptable) and save a little.