A scale of 1cm:5m means that every 1cm on the paper represents 5m on the ground.
1. If the football field is 8cm by 53cm on paper, it means on the ground, it'd be
(8 × 5)m × (53 × 5)m = 40m × 265m
2. If the hall is scaled to 7cm by 3.2cm on paper, it means on the ground, it'd be
(7 × 5)m × (3.2 × 5)m = 35m × 16m
I have reason to believe you copied the first question wrongly. You may however, edit your question so that I can update your answer.