Help me. brain tumor removed a month ago. they found a black mark of my brain what does it mean good or bad?

Not certain: It is unclear based on the information provided. But it sounds like the follow-up MRI scan demonstrated a black area where there had previously been tumor. Generally, tumors enhance or appear white when given contrast. If the original tumor did that, then this would suggest a void or lack of tumor. You should get more details from your neurosurgeon.

?melanoma?: I'm forced to guess here. Brain tumors are not usually black. If you have a history of melanoma of the skin, it may have spread (metastasized) to your brain, and if the metastatic tumor made melanin (many don't) it could appear to be a "black spot" or "block mark" on the brain. If that is not what was meant then i would need more information to give a sensible answer.