How to tell if my struts are shot!!!

I am thinking that my struts are no good how can I tell if they are? I don't see any leaks .
When I go over a speed bump it almost sounds like they bottom out ( Hitting the ground) My windshield has recently cracked from both bottom corners going up to the roof . aswell as my dash cracking in that one spot where they all seem to crack. and I think my engine mounts are bad as well .I don't notice ant change if I have it on firm or soft ride .
The guy at the parts store said that I can install regular struts and don't need the ones that adjust with the fancy soft/firm.
Thanks for any input.

Push down on one corner of the car.

It should bounce up once...returning to static height and then stop. If it moves up and down and.....you could use a better shock at that corner, at the least. Repeat at other corners if you need more convincing.

If you happen to know how many miles are on the ones in the car now, consider replacing any that have already seen at least 60,000 miles. If you still need convincing, you can always get the car on a lift, and drop the bottom end of one or more to check for leaks, dents, missing bushings, etc. See how easy it is to compress by hand.

Also look for tire wear that indicates worn shocks/suspension. Shocks and bushings aren't there just to cush your tush

Other owners have abandoned the 'automatic ride control' system. I have a 35th and would prefer to keep stock systems intact.

Work with whomever you purchase shocks from to pick something that fits your needs and budget.

Ken