I finished it not so long ago, now i'm playing the second encounter. I bought "Serious sam classics: revolution" from steam, i used proton 11 to run it but i encountered a problem where the game stuck at a "Waiting for connection" problem that was caused by the engine's timer. I found a link to pached (dll file) in protondb (SSC:R page) which i replaced the original with and it is working fine ever since.