Time Signature change moves items

Hello! Im working with video (animation). I want a faster tempo at the beginning but when i do that every midi/audio track moves to wrong places. What should I do?

If your track is tempo based, changing the time signature at the beginning logically moves everything that comes after the time signature.

Reaper 5 (maybe later v4) will have changes to Beats(position, length, rate) timebase and Time Sig changes. See Help menu for timebase help. This thread might explain a bit.