Bought a 1980 Vanagon from a private seller. How screwed am I?

I'm not a car person by any stretch of the imagination. Long story short, I need a vehicle to make short trips so I went on FB Marketplace and searched VW Bus, because I've always thought they were cool and wanted a smaller van for day trips and stuff. The perfect listing came up for a 1980 Vanagon that looked in good condition and had a ton of work done to it per photocopies of mechanic receipt.

I called the guy to meet and went to check it out. He let me drive around town with him and, I swear the thing drove like a dream. Other than me fumbling with the manual transmission for a bit, it had no issues. The guy mentioned that it did have issues with idling and that I would have to warm it up before the engine would run without stalling. On our drive, I did not experience this at all.

I looking at the engine and whatnot and, once again I'm not an automotive person, bur things look proper. No major wear or anything. I bought it for a couple grand.

The drive home was great. I had one stall while idle and I finally understood what the guy was talking about. Still, it drove the twenty miles home just fine.

This morning I drove it to work and started experiencing far more stalls. Still, once I made it to a main road, things evened out and I had no more major issues. The van drives great when it's working properly.

Now here's where I feel like I completely fucked up. The drive home from work was horrendous. I cannot break in this thing without it stalling. I have to basically restart the van every time I slow down. What did I do!? I am rusty with manual transmissions but i don't know if I'm seriously doing something stupid or wrong. I have no idea how things could have worsened so quickly.

Any advice? I can answer questions as best as I can but, if you can't tell, I'm kind of an idiot.