Overpowered Slime Friend from canister

I have used goo canister near slime pit. My new friendly slime killed every slime near the pit as I lured them with gunshots. The brain came out and to my surprise, my slime friend was fighting him for solid hours after I notice they did no damage to one another. I shot the brain and decided to explore nearest town. I lured some zombies from town near my slime and to my surprise he pretty much one punched every zombie that came from the city. His speed was “a lot more faster that yours” when I checked him. That didn’t made him move faster, just “jumped” to the nearest zombie and killed him same time he did so. I decide to debug some hulks and other high tier monsters and he killed almost all of them. Thing that killed him finally was Mi-go giant hulk thing idk the name. My question is, do the slime leveled up by killing everything? He grew to big slime but that was all, after death couple smaller one appeared. Can I make him follow me and not just wonder around?