This is my donor area (4000 grafts) after hair transplant. Is it good till now? Especially at the sides (Photo)

Your donor area will always look "thinner" proportionate to the number of hairs taken out after a FUE harvesting surgery.  The hairs will NOT grow back from the donor area (where it was taken).

Although there is no pre-op photo for comparison the donor area appears thin (probably from overharvesting),particularly the right side.

I am hoping there is considerable shock loss in this extraction donor. Because if this is actually all extraction you have been over harvested. Shock loss will return in about 3 months. The best way to correct this issue from a none experienced clinic is to decrease the density from the the most dense places and add that to your recipient and then get a scalp micro pigmentation to darken your donor. This is a great option and you will not look so thin in the donor.