Right now, I use Handbrake as the best free option for that intent. It can be downloaded here: https://handbrake.fr/
The program is pretty much straight forward on what to adjust. But I will give here the main steps to proceed when attempting to reduce the size of your video file:
On the tab Summary, set the video to be "Web Optimized"
On the tab Video, you can reduce the frame rate (24 to 30. I usually go with 30 for Tibia), adjust codecs and usually H.264 (x264) may fit well on my experiments. Set the quality on Constant Quality and adjust the bar to the number 22.
Optional: You can adjust the encoder preset to Fast. I saw that letting this stay on medium is he best option usually in order t osave the quality of the recording.
After doing that, on the lower end of the window of the program, you can pick the place on where to save the new video. After that, click the Start Encode button and wait for the encoding. By the end of the process, you video should have a noticeable reduction of it's original size.
Keep in mind that you can adjust bitrate and framerate settings on your recording program already. Try always to adjust a good quality of video that will not sacrifice lots of GB. The key here is to find balance on the recording right away.