After a month of hard work I have to pay quite a lot of things. I just got one about 200$ to invest in bitcoin. Should or should not. Please help me !

Invest your excess amount so that if it will loose you will not regret. Think wisely before you invest in bitcoin. Be sure that the price is lower than before you invest so that if it will goes high, you will gain more profits. After all, your decision is in your hand, no matter what we say you will do what you will think that is better to you.
Correct which only op do have the full control of his funds and he should really be sensible on spending his money but we should always remember on the priorities in life just like on having a savings and the rest would be put in investments like on bitcoin. as being said we should only put on the amount that we can afford to loose. $200 per month is already big here on my country and for an average person it would already be hard to save those amounts.