"I davka haven't seen that movie."
I purposely haven't seen that movie.
I specifically have NOT seen that movie.
"He doesn't eat peanut butter, b'shita"
He doesn't eat peanut butter, on principle. (or "as a matter of principle").
"Mamash" in proper Hebrew usage should translate as "tangible"; that works sometimes.
"He's mamash the biggest masmid I've ever seen"
He's seriously / honestly the most diligent student I've ever seen.
Or if we allow a sacrifice to colloquial usage and disregard proper grammar,
He's literally the most diligent student I've ever seen.
Unless you're a valley girl, (California yeshivish?) in which case it's:
He's like, totally the most diligent dude I've, like, ever seen.
"Aderaba / pum fakert, summer is the BEST time for holding by cholent."
On the contrary (or au contraire), summer is the best time to be in the mood for stew.
(The prescriptivist squad tells me this is supposed to be punkt fakert, but I'm writing them as I normally hear them.)
(Best asked with a bewildered look on one's face.)
"He is takke matir"
He in fact allows it ; or As a matter of fact, he allows it.
"He lahadam'd the whole parsha"
He flat-out denied the entire incident.
"The gantza inyan is a shtickel shvach"
The whole notion is a bit weak.
"Is it davka this maysa, or is he stam azoi a macha'os-dika guy?"
Is it specifically this episode, or is he more generally a protest-loving kind of person?
"His svora is (mamash) gishmack."
His logical argument is (totally) cool.
"Was there ever a havamina (hava amina) that the shidduch was shayach? Or that he'd become a chosson?"
Was there ever the slightest notion that they'd make a feasible couple? Or that he'd get engaged?
"For me you opened the door? Shkoyach!"
You opened the door for me? Thank you!
"Is there an inyan of wearing a hat and jacket?"
Is it of halachic value to wear a hat and jacket?