Since Marvin being on his way back to the Haven is not that far into the past and still currently ongoing it needs to be put slightly different:
"Just hurry, he can't have gone far."


To better convey the definite non-negotiabilty of Cortez' statement I'd propose:
"In fact, YOU are the one who's going to deal with it."


Again, no idea what the original line in Polish is saying in place of "whole Coyote", but in order for it to make sense maybe just put it like this:
"Never heard of this Coyote before."

Small inconsequential detail, but the bodyguard is clearly not sitting right next to Antonio, so if at all it should be:
"...one of the bodyguards was standing right next to him..."

Or to better convey that the bodyguard actively prevents Marvin from getting close to Antonio:
"...one of the bodyguards was blocking off any attempt to get closer to him..."


Not the best choice of wording for what I guess is meant to say that Antonio is not the mastermind/the one responsible for the operation? How about putting it like this instead:
"I don't think Antonio is the one pulling the strings."


Don't think that "bums" is an accurate description for Coyote's entourage of "scummy types", wouldn't "thugs" be more appropriate?
"He had a whole bunch of thugs with him."

Technically not wrong, but leaving out "of" between "hiring" and "guards" makes it sound/read more natural I guess:
"Antonio and hiring guards?"


Needs the third person singular "s" at the end of "hire":
"...and now he hires himself a small army!"


The emphasis/stress is on the number of bodyguards ("were") rather than the location ("there"), thus I think it's better to put "were there" in reverse order:
"Were you able to count how many there were?"

Should be plural "bodyguards":
"...to one of his bodyguards."


A more precise and also shorter way to put it that there's nothing to gain for Coyote to outright kill Antonio probably would be:
"There's no point in killing him..."


Several things that need resp. I'd suggest to be put a little different:
"Had they noticed you being nervous, they surely would have concluded that you suspected something. Then you would have ended up exactly like your predecessor."

Since the cave where the exchanges are taking place has already been established it makes more sense to be "the cave" instead:
"You will lead them to the cave..."


I'd rather put it this way instead, also leaving out "today" altogether (unless there's context I'm not aware of yet and this actually was "today's free lesson" with more to follow later?):
"Consider it a free lesson in doing business."


That it took Cortez quite a while learning the ropes of doing business I don't think that "a nice couple of months" is the ideal way to put it? Instead I'd propose (also replacing "it" with "that" for greater emphasis on "that lesson"):
"It took me quite a few months to learn that..."

Should be plural "they're" and "them" instead, since it's referencing the aforementioned "goods" (one orders the goods, not the delivery of the goods):
"Add that if they're not ready by tomorrow, I'll order them from a competitor."


I think "circles" is conveying the idea of "specific (interest) groups" better:
"In the right circles, of course.


The temptation to go for "the gold" is still just a probability and despite Cortez' expectations can still turn out the other way around, therefore I think this needs to be worded differently:
"...they certainly should be tempted to go for the gold."

Could be more on the point in regards to not inadvertently talk about things that would blow it and the setting of the trap be for nothing:
"Just make sure you don't let anything slip!"

Also, "bringing those damned thieves to the cave" in the first place surely is the actual concern, the logical consequence of them entering and getting "into" the cave afterwards doesn't need any explicit mention:
"...he's supposed to bring those damned thieves to the cave."


"Smuggler" needs to be replaced with "Coyote" here:
"...lead them to the cave where I made the exchange with Coyote."

"He does not like something.", while technically correct, doesn't come across as how a cutthroat like Coyote would mock Marvin for being overly pedantic? I'd suggest putting it this way instead:
"Something's not to his liking."

"Someone's trying to swindle the captain out of supplying provisions to the Haven" is not what's actually happening though?
Neither is Cortez "supplying provisions to the Haven" (that would be Antonio) nor is Cortez swindled out of "provisions to the Haven" (but a share of the money for the delivered provisions instead).
Therefore it should be:
"Someone's swindling the captain out of money for the provisions delivered to the Haven."


It's also an ongoing issue that occurred at least once before (Cortez mentioned the last messenger before Marvin who "didn't come back") so Coyote and the "bodyguards" are not "trying to swindle" or "trying to steal", they already have successfully done so, as mentioned, at least once. They're not trying, they're doing it.
Therefore the corresponding log entry also should be:
"Cortez didn't like that someone is stealing from him."