There are several reasons for this issue
If your device does not have sufficient processing power e.g. RAM or Processor, video editing tasks can be slow. If your Android version is less than 7.0. Editing high-resolution videos or working with large file sizes can slow down the editing process. Using outdated versions of the Inshot app may lead to performance issues. You need to update your RAM, Processor, and Operating Software and install an updated version of Inshot to resolve this problem.