Windows that won't open or are jammed shut usually indicates the lock mechanisms are broken, if you can push the window top or bottom & one half of it moves & the other half doesn't, the same being jammed left to right then the centre of the lock mech is broken. I can get this open with the correct tools and be replaced with new parts.
Windows that won't shut or are gapping in the corners usually indicates that the window hinges are broken or faulty. If you can get the tip of your fingers in the corners & feel draft nows the time to replace them. Child restricted hinges can be fitted & only open so far, if you're concerned about the window flying opening or your child falling out.
Handles on windows and doors can all be replaced if damaged or broken.
If your PVC door or patio multipoint lock is jammed, broken or feels faulty this can all be replaced with new parts.
Blown glass / condensation can be unsightly to look at & will only get worse over time with hot & cold wheather,this is only cosmetic but there's nothing worse than looking out a foggy / misted steamed up window.
Euro cylinders / barrells can all be replaced with knew keys & upgraded to anti snap / anti pick / anti drill / anti bump if your worried about security.
Cat flaps in glass / panels
Dropped doors / windows
Patio wheels, tracks & locks
Extra security where needed