Vw polo drivers side floor wet, front and back?

Check the firewall area...get the garden hose, and let it watering down your windshield and watch of where the water drains down to...and look into those area, you would likely find the leak.

squirt it out with a hose or spray wand from a car wash place..

drains plugged up? flush with hose or pressure wand at car wash..

check front and back wind shields some times cars and trucks from bumps and stuff from ware the seals in the top corners that giud the water off gets pin holes and a vacume can acure sucking water inside and seats floor dash head liner gets damage take it to a windshield repare shop and have a vacume test done sometimes some places will not charge you please ask them first

Sounds like the door gasket or trunk gasket is not sealing.
You may have to take it to a body shop to find the problem.

Dies car have a sunroof? If so, sunroof drain is clogged and backing up into car.

Gear lever usually if it is mounted on the floor console

i had this problem too. it was a small rust hole in the wheel well. i took a pieace of aluminum flashing and a can of spray bedliner for trucks and patched it up. it works great! just a thought for you