Find and correct the mistake in each sentence.
1 When he was young, my dad used to reading books about nature.
2 When I got to the house, there was no one there. The party finished!
3 I am running in the park every morning before school.
4 We're really excited because we will go on holiday next week.
5 He was tired because he had been running two kilometres.
6 While I was cycling in the park, I was falling off my bicycle.​