fast 改：faster
than是表示比较,前面要用形容词或副词的比较级啊,fast是副词的原形,所以要变成faster
a few weeks 改成：in a few weeks
在几星期之后,用于一般将来时要加介词in可以用英文来陈述原因么?不要有语法错误...A comparative degree should be used in front to than, which always leads to an adverbial clause of comparison.But fast is the primary form instead of a comparative degree.So it should be changed to faster.In the simple future tense, there should not omit in front of "a few weeks" the prep. in.Just add the prep of In.