The windows of the doors can be electric or with a crank, in any case to slide them more easily it is enough to "dirty" the seal with talc.
It may happen that they jammed, in this case it will be necessary to dismantle the internal panel of the door and check the reason for the lock from the inside.
This can be caused by the fact that the internal guides have gone out of register and it will therefore be necessary to readjust them.
Or the lowering mechanism has some problems, in this case it will be necessary to check the play of the levers and if electric, the operation of the motor.
When adjusting the registers, make sure that the glass slides easily in the guides.
Over time the window seals tend to dry out, we will notice this effect because they will tend to shorten and there will be more space between the glass and the gasket.
In these cases there could be an excessive penetration of the water in the door in case of rain which in the long run could damage the door but also the stereo and electrical systems found in the door.
Replace the gaskets and always treat them with the appropriate products to maintain their elasticity.