Hello @DeDoopys 

Thanks for posting about this.  Strava does calculations on the raw data imported and doesn't re-report totals calculated by other Apps and devices.  For that reason, it's expected to see some small discrepancies across Apps/platforms.

You don't mention what device you're recording with, or what sport (running, cycling etc.)  Often times, these discrepancies are at least partially due to moving time calculations.  You can find out more about that here

I hope that's helpful information and please let us know if you have more questions.

Hello Jane,
I have used several imports, both MapmyRun and Garmin Connect and from both my running times are adjusted.
The strange thing is that I have looked at running friends, and there the times from Strava and for example Garmin are the same. Would I have a setting somewhere wrong, that Strava adjusts this? Thanks again for your response.

It can be due to luck that your friends sometimes have the same time in Strava and Garmin,  they can have another auto pause threshold setup in their Garmin device so that their times come nearer to that calculated by Strava or their GPS is more precise.