Thank you for answers

I like hotels.com
after 10 nights - you get 1 night for 'free' + for every night and for ''free night'' you get miles.

A lot of miles you can get from PINS, for each Euro you get 6 Points, so if you book 10 nights (for example 150 euro per night) you get 9000 Points + 1 free night (for this night you will get another 900 points). Finally with 10 000 points you can already get a free flight, however they have not a lot of routes.

So the same you can get with AsiaMiles or KoreanAir.

I tried to find the same manipulations for other big companies (EU or US). Found a few, however only with booking.com / also expedia. But they do not offer you the same deal like ''free night'' + you get only 1 Mile for 2 EURO.

rocketmiles.com and kaligo.com did not try, but prices there are far from 'the best'.

I saw that Avios worked with hotels.com a few years ago. may be in future something change again.