Help With Information On Several Austrian / German Covers

Hello, I am a long time collector of Newfoundland and happened to buy a handful of Austrian or German or Polish covers from a recent visit of mine to Vienna.

I'm looking for any guidance on the stamp details, where the letters went to and from and a sense of value. These are my guesses of this covers (but could be wrong)

1. A postcard with Vienna (Wien) from 1891.

2. A cover from Germany? (Feldpost) to Austria October 4, 1941. Note the Nazi cancel. There is a letter inside included, which I translated and can share if anyone is interested.

3. Another cover from this era (WWII) - I believe it is to and from Austria in 1941; also a Nazi cancel. I also have this letter, included and I can share the English translation if need be.

4. Another WWII cover : From Poland to Vienna March 20, 1944. Based on the cancel, my research suggests it was posted from Ost Radom in Poland; During this time it was a Jewish Ghetto and prison camp area under the Nazis. Though by this date, majority of Jews had been deported to extermination camps. I also have the letter and translation upon request.

Here is the second one...

Here is the 3rd cover:

Here is the 4th cover:

I have English translations of each.

Please share with me the community knows about these:
1. What is the stamp #?
2. What years ?
3. Approximate value ? (I'm looking to trade or sell them)
Thanks

Does anyone want these? Just email me and if you cover the postage, I will send them free. Thanks

Hello again,
If anyone wants these covers, please contact me and I will post them to you for no charge. Just want to find a home for them.
Thanks