garmin watch are worst in indoor walk

Did you use the calibration after each walk?

There is no calinration on indoor walk

I just experienced the same thing with treadmill. I did calibration twice. It’s always off. 

To get accurate data for indoor activities you need to make always the same step(length) and you need to move the wrist in the same way.

If you raise your wrist to check the watch you're already affecting the data...if you do a shorter or longer step than what's the average step you're, again, affecting the final result.

The same goes for the treadmill...you can run with a constant speed set but if you make longer or shorter steps the watch will consider it as slower or faster pace.

I don't want to be against other watches but i doubt that the apple watch is more or less accurate as it should work in the same way.

Are you walking on a treadmill?