Tried to upload file on Merovingian dot club

I screen and audio recorded something on chromebook

It would not work with the webm video format it defaulted to

I do not know if there is a way to change what format it uses

I then tried using

freeconvert website to convert it to MP4

Then it complained and the phrase "1000 fps" was mentioned and it still would not upload

Is free convert website safe

https://www.freeconvert.com/mp4-converter/

What websites or Google apps safe

how many fps? file size / memory?