back on one’s feet: 恢复起来、经受打击后重新站起来
People are back on their feet after the earthquake.
人们从地震中恢复起来了。

spend…on: 在…上花钱（时间）
They spent two years (in) building this bridge.
造这座桥花了他们两年时间。
His money was spent for books.
他的钱用来买书了。

call in: 收回；拜访；召集；调入
How many friends will you call in?
你将邀请多少位朋友？

It's not a big deal: 不是什么大事
Just forget it. It's not a big deal.
算了吧。没什么大不了的。