Usually, contribute to the Polish edition of Wikipedia, mainly in the United States and Soviet/Russian submarines area.

Some of my featured articles there:

The best articles, so far	Need some improvements
pl: Los Angeles class submarines	pl: History of American & Soviet submarine launched ballistic missile systems
pl: Ohio class submarines	pl: Operation Deliberate Force
pl: UGM-133 Trident II D-5	pl: Thresher/Permit class submarines
pl: George Washington class submarines	pl: USS Nautilus (SSN-571)
pl: Seawolf class submarines	pl: USS Thresher (SSN-593)
pl: USS Albacore (AGSS-569)	pl: USS Freedom (LCS-1)
pl: Skipjack class submarine	pl: XXI class submarines
pl: Submarine	pl: Project 941 subamrines
pl: History of submarines	pl: Ballistic missile