一个英语句子的结构分析----高手帮忙

一个英语句子的结构分析----高手帮忙
Then gradually between about AD 800 and 1150,English became less like German because those who ruled England spoken first Danish and later French.
1、分析前半句句子结构“Then gradually between about AD 800 and 1150,”
2、我想知道because在此是连词还是介词?我总觉得是是介词,因为后面不是一个句子.有个定语从句我知道.反正是有点迷惑.