Do brain tumors always cause symptoms? if so what are they and are they multiple symptoms?

Not always: Depends on location, size, growth, type of tumor, surrounding edema (swelling) and probably other things.

No: Some brain tumors cause no symptoms and are discovered incidentally when a head scan is done for other reasons, such as after a car accident. There are many different symptoms a brain tumor may cause, from just headache to seizures to focal weakness or sensory loss to confusion to other neurological problems such as difficulty with language.