Though sun is not the biggest or brightest star, it appears so because it is the nearest star from us. Since the distance is very less, it appears bigger and brighter. As the distance of other stars from us increases, their brightness and size appears to less.
Hope it's help U
because it is farther away
Coz it is very close to us. Hence it is very far from us but it's shine and heat is enough for us even after such distance
and we all know the fact that closer objects appears bigger than faraway abjects