Liquid-filled bubbles in lower part and under my left feet, as well at right fingers. the liquid is clear and goes and comes, mostly around the heel. ?

Eczema or Simplex: Skin with 'bubbles or blisters' may be dyshidrotic eczema which is common on hands and feet. It may be due to contact to an allergic agent so the strategy is to find/remove the offending allergen. Another possiblity is a manifestation if herpes simplex. You should see your primary care doctor or dermatologist for confirmation.

Several things: It could be blisters, tinea, contact dermatis, infection. It should be esamined and the fluid cultured for infection.