Hi ​@MateuszRider, what does the gps recording look like? Is the generated map accurate? Perhaps you can post a link to one of problematic activities here. 
 

in general, what you can do is to try the “Correct Distance” feature. You'll need to open the activity on the Strava website (not the mobile app), then in the menu on the left, click the three dots, and then Correct Distance. That will recalculate the activity based on the map data; and it's reversible if you're not happy with the result. But keep in mind it's only useful if the actual gps data is somewhat accurate. 

Yes the map looks good and on the other app the distance and speed is accurate but somewhere down the line when it gets uploaded to strava it totally changes everything 

Hi ​@MateuszRider 

Thanks for your post. I would recommend switching your distance stream to see if that resolves the issue:

In some situations you can change the distance that is shown for your activity. Changing the distance stream may also update the pace or duration of an activity. If your device created a distance stream using sensors such as a speed sensor, pedometer, or accelerometer, you can switch your distance on Strava to use GPS data rather than the generated distance stream.

To swap your distance stream:

• Go to your activity page on the website (this feature is currently not accessible in our mobile apps)
• From the activity page click on (◦◦◦) the more options menu > Correct Distance.
• From the pop-up, click "Correct Distance".
• When the status changes from "Calculating" to "Updated," refresh the page.

If you would like to revert the change, you can click the same link and click "Revert Distance".
 

For more information, see our article on How distance is calculated for your activity. 

Thanks for this helpful information ​@Jane !

My (WearOS watch) recordings looked fine on the map, but distance and (therefore) avg speed were off by roughly 50%.

I was able to use the “Options - Correct Distance” fix to fix them, but would I have to do that for every single activity or is there a way to have Strava do this by default?

It would seem there’s a bug somewhere though, since 50% off feels like a lot (I recorded the same activity on my phone and that recording was shown correctly on Strava without fixing/“Correct Distance”...

Jorik.

Jorik, I am having the same issue.

Walking, biking, and running are fine but for certain activities like inline skating the speed and distance are extremely low.

Did you ever find a way to report a bug?

Hi Kody, sorry no, I have not.

BTW my earlier reply to your topic/bug report is still under review ;)

(is just a confirmation that we experience the same issue)

Mine is the same!