Working With Multiple Frame Rates.

Hi Guys, I am currently working on a small project.

The project contains multiple video files that are different frame rates. As you can understand this makes editing difficult (as frames are frozen or skipped altogether)

How do make it so that I can work with multiple video files of different frame rates so that I can complete this project amicably?

Please Note I am going to export the video, so is there anyway I can change the frame rate of the selected files so that I can upload the video without sacrificing quality.

Thanks (in advance) guys.