I replace the power steering pump on my volkswagen passat 2001 and is making kind of squealing

better to replace if kinked just disconect form both ends wherever its conected put new pipe on refill power assist resivwar and turn steering lock to lock when started

excess mechanical drag from the pump can cause the belt to slip and squeal, but before focusing on the pump I'd check the condition, tension and alignment of the belt. I might even try cleaning all the pulleys with an aerosol brake cleaner and install a new belt, particularly if the current one has more than 50,000 miles on it. It might be that the squeal is coming from or caused by a different belt-driven accessory.
A more typical noise from a power-steering pump is a high-pitched whine, not a squeal. Usually, if the steering wheel is stationary, meaning that the steering rack is not "asking" for assistance from the high-pressure fluid from the pump, there's little or no noise

Is it tougher to turn the wheel than it was before?

VW Passat year 1999 use a power steering fluid type G 002 000.

A quick way to check for belt squeal is to crank the engine, open the hood, and get a can of WD-40. Spray the belts, this will cause the belt to temporarily quit squealing. Note that the squeal could be from a bearing from power steering pump, air conditioner, alternator, or anything else that has a bearing. Another thing to pay close attention to is the tension pulley, they will be a distinct squealing sound before going out and that may be your whole problem.

check power steering fluid level

I'd guess wheel bearing is bad.

alternator may be starting to fail dont trustit have diagnosed by qaulified tech.

low power steering fluid/ bad power steering pump

If this is a front wheel drive car I would look at the CV joints