Slowness & crashing on an existing file

Hi there

I was given a file to edit by a friend, I do not use Premiere on a regular basis. The file is, I'm assuming, badly organized and this or some other issue makes it slow/buffer often and it's been crashing every 10-15 minutes or so.  Occasionally an error comes up 'Error retrieving frame 1973 from time from the file. substituting frame'. and this repeats. I'm assuming these are related to the crashes.

Any tips you can give me on how someone who's not familiar with Premiere can do sort of easily to help with this error/these problems would be helpful, thanks.