[sharbeldam]

Can someone explain the overlapping in NMR, like give me a simple rule for it? if i were to decide, there 4 hydrogens are not symmetrical so we should get 4 peaks, why did they merge the 3 hydrogens on the left side of the ring in one peak? please if there is a simple rule, i would like it if someone tell me when to do that. (btw there is 1 mistake in the question, that 3H,s should be 1H,s)

[Babcock_Hall]

The situation is not simple, but if you are a chemistry major, you might learn about this topic in an advanced undergraduate class or a graduate class.  What is taught in the first year of organic chemistry are the first order rules of coupling.  They are not followed when the difference in chemical shift (in Hz) between two nuclei is on the same order of magnitude as the coupling constant J, also in Hz.  The word "multiplet" covers situations like this.

[sharbeldam]

I understand , thank you
so basically there is no simple rule, you just to figure out the difference to know if they would overlap or not.

[Babcock_Hall]

If you want to start working on the topic on your own, read up on magnetic equivalence or nonequivalence.