Learn Hardcore Polish: On umie mieszać zupę powoli i kroi chleb szybko. - He knows how to stir soup slowly and cuts bread quickly.

It’s grammatical: umie mieszać zupę powoli (ability) + kroi chleb szybko (a general fact/habit). Polish lets you coordinate different predicate types with i. For a tighter, more parallel style, either:

Ability for both: On umie mieszać zupę powoli i kroić chleb szybko.
Plain statements: On miesza zupę powoli i kroi chleb szybko.

If I want both parts to be about ability, do I have to repeat umie?

No. On umie mieszać zupę powoli i kroić chleb szybko is enough; one umie governs both infinitives. Repeating (… i umie kroić …) is also correct, but adds emphasis.

Why is it zupę and not zupa?

Because it’s a direct object in the accusative case. Zupa is feminine; its accusative singular is zupę. Verbs like mieszać take a direct object in the accusative: mieszać (co?) zupę.

Why does chleb stay the same?

Chleb is a masculine inanimate noun; in the singular its accusative form is identical to the nominative: chleb. So you get kroi (co?) chleb with no ending change.

Why is it kroi and not kroje?

Because kroi is 3rd person singular. The verb kroić (to cut/slice) conjugates:

ja kroję
ty kroisz
on/ona/ono kroi Notice 1st person has -ę, while 3rd person is -i.

Where can the adverbs go? Is kroi chleb szybko the only natural order?

Adverb placement is flexible. Common, natural options include:

On szybko kroi chleb.
On kroi chleb szybko.
On kroi szybko chleb. (also fine, a bit more marked) Put the adverb close to the verb it modifies. Similarly: On powoli miesza zupę / On miesza zupę powoli.

Would a be better than i here because of the contrast (slowly vs quickly)?

Often yes. A highlights contrast, while i is a neutral “and.” You could say: On miesza zupę powoli, a kroi chleb szybko. That reads very naturally with the opposing adverbs. Note the comma before a.

Can I drop On?

Yes. Subject pronouns are usually omitted when context makes them clear. Umie mieszać zupę powoli i kroi chleb szybko is perfectly normal. Keep On for emphasis or contrast (e.g., “He, as opposed to others…”).

Does Polish present tense mean “is cutting” or “cuts”?

Both. On kroi chleb can mean “He is cutting bread” (right now) or “He cuts bread” (habitually). Context decides. The ability part umie is also present tense (“knows how to/can [by skill]”).

Should there be a comma before i?

No. In Polish you normally don’t put a comma before i when it links coordinated parts of the same sentence: … powoli i kroi chleb szybko (no comma). If you use a for contrast, you do add a comma: …, a kroi chleb szybko.

What’s the difference between umie, potrafi, and może?

umie: knows how to (learned skill), very common and neutral.
potrafi: is capable of, can manage (often implies achieving/being able to do something in a given situation).
może: may/is allowed/can (permission or external possibility), not used to express a learned skill.
For ability here, use umie or potrafi: On umie/potrafi kroić chleb szybko.

What about aspect: kroić/pokroić and mieszać/zamieszać?

kroić (imperfective) = be cutting/used to cut; pokroić (perfective) = cut up to completion. Present of a perfective refers to the future: On pokroi chleb szybko = “He will cut (it all) quickly.”
mieszać (imperfective) = be stirring/keep stirring; zamieszać (perfective) = give it a (single) stir/start to stir.
For ongoing manner (“slowly/quickly”), imperfective is the default.

Are there articles like “the/a” for zupa and chleb?

Polish has no articles. Zupę/chleb can mean “the soup/bread” or “some soup/bread,” depending on context.

Is powoli the only word for “slowly”? What about wolno?

Both exist, but use them carefully:

powoli = slowly (everyday, unambiguous).
wolno can mean “slowly,” but more often means “it is permitted” (e.g., Tu nie wolno palić = “It’s not allowed to smoke here”). To avoid ambiguity, powoli is the safer choice.

Is using umie with something as basic as “stir soup” idiomatic?

It’s grammatically fine, but umie typically highlights a skill worth mentioning (e.g., umie gotować, umie kroić bardzo cienko). In everyday speech you’d more often just describe what he does: On miesza zupę powoli i kroi chleb szybko.

Any quick pronunciation tips for tricky bits?

ch in chleb is like a voiceless h.
ł in powoli is like English w.
sz in mieszać is like English sh.
Final -ę in zupę is a nasalized “e,” often realized lightly as “eh” before a consonant.
Stress is almost always on the penultimate syllable: o-NU-me, MIE-szać, ZU-pę, po-WO-li, KRO-i, chleb, SZYB-ko.