Air movement, the best way to combat petal blight is with good air movement, especially when the plant is indoors. I keep a cheap, 7 inch fan in the general area of my indoor plants, the fan blows a breeze across their area. Grassy leaved plants all have leaves moving at least a little bit in the breeze. A buoyant atmosphere is idea. Outdoors make sure the azalea is not crowded by other plants. Up on a shelf is best. Note: the fan is left running, 24 hours a day, seven days a week.
Do I take all the damaged flowers off and will they grow back this year??
Yes, remove damaged flowers.. No, the flowers will not be replaced this year. Other buds that have not opened will continue to open, but the ones you remove are gone, done, and will not be replaced.
New growth this year will in autumn make the buds for next year's bloom. So loosing flowers this year to blight will not affect next year's bloom. Next year can be normal.
And do I need to repot it I’m sorry for all the questions but I tired to do research on the web but couldn’t find all the answers
Only repot if the potting media does not drain freely. When you water, the water should sink right in to the mix. IT should not pool on the soil surface. If your pot is still free draining, there is no need to repot. If you repot while the tree is in bloom, all the flowers will drop off. It is not recommended to repot an azalea in bloom. If you feel you must repot, cut off all the remaining flowers, and unopened buds. Never repot a blooming azalea without removing the flowers.
But repotting will not help the petal blight situation, so don'e worry about repotting until a week or two after all the flowers are done.