"see to it that..."就是"make sure that..."的意思,确保,务使.

Can you see to it that the fax goes this afternoon? 你保证今天下午就把传真发出去,行吗?

4.He feels like he's on a losing streak. 他觉得自己总是在失败.

Streak就是中文里"手气,运气"的意思. 而on a losing streak就是指手气不好,手气背,老是输的意思.

a streak of good luck 运气好的一段时间
to hit(= have)a winning streak 碰上顺的时候
a lucky/unlucky streak 运气好╱不好的阶段

5.As you know, the winner gets a big party, and they can invite whoever they want, which could go a long way in helping her fit in.你知道,获胜者将会得到一个庆祝晚会,他们想请谁就能请谁,这对于帮助她融入集体有很大作用.

"go a long way in/towards doing sth:就是对做某事帮助很大的意思.

The new law goes a long way towards solving the problem. 新的法律十分有助于解决这一问题.