Try spraying the seals with Autoglym vinyl and rubber care, softens them up. Done mine made a difference. If that does not work then it's get a guy in to renew seals of opening windows.
Before you get into seals, Math, see if there's any adjustment on the hinges. uPVC doors have all kinds of fine-tuning features. Your windows may well have as well. See if you can find a uPVC-savvy carpenter locally.