Trying to edit recorded 30fps mkv clips. Seen as 1000fps in blender.

Hey! I have a major problem. I have hours of recordings of a gameplay. I want to make a compilation of them with help of blender video editor.

All the recordings were done to mkv with 30fps. But MS explorer sees them as 1000fps. And so do I think blender does. When playing in VLC they freeze the player off but they work completely fine with windows 10 video player, even on skipping. Nothing seems wrong with the recordings there.

Now the main problem.
When I add these clips in blender the video clip is horribly long. The sound clip seems fine and also got correct length. When I use speed changer on the video clip to stretch it to the length of the sound it makes the playback performance horrible. Im also unable to do major editing as blender fails or lags horrible whenever I try to select a part of the timeline.

I also tried to add a clip. Add the speedchanger and see if blender just can export/render it in mp4 format or Avi format to reuse that for the editing. Blender slows down every second of the rendering until it stops completely.

Is there any way I would be able to edit these mkv files? Right now it seems impossible. And I dont have any other programs to do this with. I tried to download this davinci program once but it lacks support for other filetypes I have. And I cant afford any expensive editing programs (neither do I make videos often) I just want this to work in blender as video editing has worked fine for me in the past with other filetypes.