3 weeks after liposuction and buttlift I can't take this faja, girdle, garment whatever. Do I need to wear this?

The most valuable information is the information from your specific surgeon - this is why people choose their specific surgeon, for their expertise and skill.  Post-operative compression garments are essential to your result. If you are having difficulty with your particular garment, you should see your surgeon and discuss alternative garments. 

Wearing of garments after liposuction can be very important depending on the type of procedure and the location.  Every physician has a different approach to post-op care, so it is important to speak to your doctor about your concerns. Garments that are excessively binding and creasing can cause issues if left unchecked.  If a garment is ill-fitting, speak to the office about options for replacement; this make mean making a visit to show your concerns.

I have found that post operative compression garments are important because they control swelling. They should be comfortable and my patients would rather wear them then feel uncomfortable due to the swelling. We provide our patient with places to order garments on line as well as stores that do fitting for garments. Most patients wear them for months and have the altered to be made smaller as the swelling goes away.