She is under a lot of paperwork.

Correction: She is swamped with paperwork.

You had better think not going home befor you fill out all these forms.

Correction: You should reconsider going home before filling out all of these forms. 

He needs to go over all documents thoroughly.

**Good and correct sentence~ ^^ 

They were hired for the marketing department.

**Good and correct sentence~ ^^ 

The concert was very high level of complement.

Correction: The concert was highly complemented. 

You have to communicate active with other departments' coworkers.

Correction: You must actively communicate with colleagues from various departments.

While those are entry-level tasks, the amount are large.

Correction: While these are entry-level duties, the number is substantial.

Making copies was my first task when I was a new employee.

**Good and correct sentence~ ^^ 

You should have headed to the bank.

**Good and correct sentence~ ^^ 

She is always intimidated the dog.

Correction: She is always afraid of the dog.

He was confident whatever he did as a kid.

Correction: Whatever he did as a child, he was sure of himself.