Morning!

I'm sure this is a newb question but I've been working 2 days straight on this short video and have decided to ask for some guidance. The leadership of my company all took videos of themselves and sent them all to me to put in a video and sync to a song. They are all different video types at different fps. I converted them all to the same frame rate of the lowest quality video clip which is 25 fps and put them in microsoft video editor and another open source video editor because I was having the same issue. They look perfect in the software but when exported to an mp4 720p at 25fps the sync is off for 20-30 seconds about a third of the way and then finally catches up.

This is my first time doing this and have read a ton at this point the frustration is emence and looking for some help! Thank you!