why when i play part 1 i instantly get to the ending
?

where part 4?

Does it require anything? I got some error texture.

Not bad game like the three parts, only thing is some parts of the game is not clear what to do, and also when you pick an item up like a box it kills you that a bit silly so need more work.

Map overall isn't too bad, occasional circular arena besides. A few bits and pieces of scripting issues too, but the only real issue by far is...just, holy crap the sheer number of janky "nothing personal, kid" right-behind-the-player spawns is a tad loco.

Ugh... Between the Zombine in enclosed spaces and the "combination of poison + fast headcrabs that's basically an unavoidable instakill" spam, I can see why he deemed these maps "not good". (Fun fact: Apparently Zombine in Gmod use player grenades, which deal 125 damage, instead of their usual 75-damage grenades in HL2. Which I found out by collecting chickens and reading the Wiki...)