Changing a videos frame rate can be easily done with FFmpeg. From the official FFmpeg documentation to change frame rate
-filter:v fps=fps=25 is required. If inputvideo.mp4 was 60fps and I wanted to make it 30fps I would use this:
ffmpeg -i inputvideo.mp4 -filter:v fps=fps=30 inputvideo_30fps.mp4
To change framerate whilst encoding a video with FFmpeg:
ffmpeg -i inputvideo.mp4 -filter:v fps=fps=30 -c:v libx264 -preset fast -crf 23 output.mp4
That will make the video 30fps and encoded with fast 23.