I was wondering what are the signs of brain cancer/tumor?

Depends on location: The general signs of a brain tumor/cancer are those of mass effect. That is, seizures, headache, motor weakness and speech or language problems (if it is near these areas of the brain). When the tumors get very large, this can lead to problems with thinking/cognition as well as lethargy and coma.

Varied Sx: Common symptoms are persistent headaches which are progressively getting worse. Nausea and vomiting is also fairly common and accompanies the headaches. Seizures are not uncommon. Any of these symptoms alone or together would raise this possibility in my mind.