Questions & Answers about Neměl bys běhat moc rychle.
In this sentence, neměl bys means you shouldn’t.
More literally, it is built from mít and a conditional form, but in practice měl bys + infinitive is a very common way to say you should + verb:
- Měl bys běhat. = You should run.
- Neměl bys běhat. = You shouldn’t run.
So here it expresses advice, not a hard command.
That is a very common point of confusion. Měl does look like the past form of mít, but here the whole construction is conditional, not past tense.
Czech forms the conditional with:
- an l-participle such as měl
- plus by / bys / bychom / byste etc.
So měl bys does not mean you had here. It means something like you should / you would be supposed to.
Bys is the 2nd person singular conditional particle, used with ty.
Very roughly, it carries the you would part of the meaning.
So:
- měl bych = I should / I would have
- měl bys = you should
- měl by = he should
Historically it comes from by jsi, and learners may sometimes see both, but bys is the normal compact form.