manifest of the Gera, he arrived here on 9 Mar 1905 and was "25 years old."
This link says he was 24 yrs old and arrived on the 12th March 1905. There certainly are discrepancies!
familysearch.org/ark:/61903/1:1:JF3M-R59
Słocina
There is also an historical area of Rzeszów called Słocina which I found under Polish Wiki:-
pl.wikipedia.org/wiki/S%C5%82ocina_(Rzesz%C3%B3w)
I think this one is far more likely to be the Słocina in question because Albert was born in Mazury, and these 2 places are very close to each other.
Mazury is the name given to a large area of Poland which includes it's well known lakes, but I found there is actually a village called Mazury too, and it's this village which is close to Słocina, about 25 kms away, so this appears to be more likely than the other Słocina which lies on the other side of Poland.
en.wikipedia.org/wiki/Mazury,_Podkarpackie_Voivodeship
Of course this is guesswork on my part, but people then generally didn't travel to the extent they do these days, unless of course they emigrated!
As regards Polish genealogy resources, there is no one central database unfortunately.
I did come across a good site called Geneteka and have looked at this briefly, entering the surname Sondej. It hasn't brought up anything specific that I can see, but you could always try entering the other names you have in it.
geneszukacz.genealodzy.pl/lang-eng
The page I have linked to is in English, but unfortunately, once you hit enter and the results are displayed, they come up in Polish. Trying to put a new page back into English doesn't work and takes you to a new page ( unless I've done something wrong which with my computer skills is quite likely! )
I don't know if you understand and can read Polish, but if you don't, once the results are shown you will see a page with the Polish provinces on the far left e.g Warmińsko-Masurskie ( listed under 'site' in English )
To the right of 'site' are listed father's details first, then mother's.
Terms you will see:-
Urodzenia - Births
Zgony - Deaths
Małżeństwa - Marriages
Chrzty - Christenings
Imię - First name
Imię Matka - Mother's first name
Imię Ojca - Father's first name
Nazwisko - Surname
Parafia - Parish
Wyszukaj - Search
Of course this is all irrelevant if you can read Polish, but thought it might save you some time translating.
I haven't read all of this thread, but remembered it was on the forum, so you might find lots of help and other Polish sources in it:-
https://polishforums.com/genealogy/poland-resources-3318/Forgot to mention, on the Geneteka results page for your chosen name, you can click on Skan on the far right for each result, which if available brings up the written document ( not all are available ). Of course it will be in Polish, but some nice kind soul on this forum might be able to translate it for you if you do find one which applies to a family member.