Can you still eat comfortably with partial upper dentures supporting 4 teeth?

Depends...: ...On the design of the partial denture, your personal ability to adapt to something "new", which teeth are remaining that the partial clasps onto, are the remaining teeth well supported or do they have gum and bone recession (periodontal disease) and mobility? A lot to think about. Talk to your dentist about your best options.

It's subjective: There is a tremendous variation between individuals as to what they are comfortable with and how they adapt to change. Removable partial dentures do not feel like your own teeth. Some patients adapt quicker and easier to change than others. Consider an implant retained replacement. Discuss your options with your dentist and\or a prosthodontist.

Possible : You can eat somewhat comfortable with 4 teeth and a thick plastic fake teeth. Partial dentures are held in by the remaining natural teeth in your mouth. Partial dentures eventually will break your natural teeth. Consider dental implants to replace your missing teeth and really will enjoy eating again.

Yes : Provided it is well made and is very stable in your mouth.