Hi, there are two ways around this.
One is that the program you use on your computer (or most of them) offer the opportunity to 'simplify' or 'resample' routes to reduce the number of points. You could do this if there are too many (instructions will depend on the program you use)
An alternative (that would only work for future walks) is to make a change to the settings on your GPS so that it records fewer points - if the files are too large it's probably recording your position every few seconds, which is really more often than you need unless you are a very fast runner
Again instructions would vary depending on what sort of GPS or phone software you are using.