Doubt about tenses to use in my resume.

"Presentations of complementary advanced topics were recquired for many final examinations. They have been prepared by looking at articles and reviews. "

"Technical writing, presentation skills, independent study were improved significantly."

"During experimental courses familiarity with electronic amplification, signal processing, and data acquisition techniques has been acquired. "

What should I use between were and has/have been? In order to mantain the third person. In both cases I feel to be repetitive.

Thanks in advance.