How could a Focke-Wulf 190 pilot see anything at all from his cockpit?
It looks like the pilots are performing taxi-runs for show. For an actual flight, by sitting on the seat pack parachute (and/or a cushion) the eye level is raised as shown below:


(warbirdsnews.com)


(worldwarphotos.info)

For how to taxi while sitting so low, it's usually down by taxiing in an S-shape or following hand signals from a marshaller.



Related:


How are aircraft controlled that have no forward view out of the cockpit?
How do pilots manage to keep aircraft on centerline during taxi?
How does a taildragger steer (taxi) differently to tricycle gear?
Would the Gee Bee be allowed to fly today, with so little forward visibility?