First of all, hi everyone. The reason why I ask for a trigger master is because I'm not really keen with triggers (yet) but I'm working on it. I am already making a level/mod but there's a twist. The twist is that the mod takes places in 1 big room where you have to complete puzzles and everytime you complete a level, new walls, floors, ceilings will replace the previous puzzle level but in the same room! I know it's sound ridiculous but hey...

Hi, welcome to the forum.

Your idea sounds interesting, but it's pretty ambitious. If this is your first mapping project, I'd start with a simpler approach.

One possibility would be to create separate rooms that look enough alike so that it seems like the room is changing, while in fact the player is seamlessly transported to the next room when they finish a puzzle. You can use trigger_teleport entities for this.

Depending on how many rooms you plan to make and their complexity, it may not be practical to put all of the rooms in one map file. To change to a different map, use trigger_changelevel. There are a couple of pitfalls when using this entity, so read the description page carefully. Especially the bit about the level changes being two-way. Also use a trigger_transition to prevent things from the previous map appearing in the next.

I hope this helps you to get going, just read the info on Valve's mapping site play with the entities a bit. If you can't figure something out, search the forum (many simple questions have already been answered) or post if you can't find the answer.