Kad imam previše stresa, tlak mi je visok.

Yes. Kad and kada both mean when here.

• Kad is shorter and very common in everyday speech.
• Kada is a bit more formal or neutral in writing.

So these are both fine:

• Kad imam previše stresa, tlak mi je visok.
• Kada imam previše stresa, tlak mi je visok.

They mean the same thing.

Because previše means too much / too many, and after it, the following noun normally goes into the genitive.

So:

• base form: stres
• genitive singular: stresa

That is why you get:

• previše stresa = too much stress

This is a very common pattern in Croatian:

• previše posla = too much work
• previše vode = too much water
• previše ljudi = too many people

Stresa is genitive singular.

The reason is not the verb imam, but the quantity word previše. Words like puno, malo, dosta, previše often require the noun after them to be in the genitive.

So in this sentence:

• imam = I have
• previše stresa = too much stress

Literally, it is something like I have too much of stress, though in natural English you would just say I have too much stress.

Here tlak means blood pressure.

On its own, tlak can mean pressure in a general sense, but in health-related everyday language it is very often understood as blood pressure.

If you want to be more explicit, you can say:

• krvni tlak = blood pressure

So this sentence could also be:

• Kad imam previše stresa, krvni tlak mi je visok.

That version is a bit more explicit, but the shorter tlak is very natural.

Mi is the unstressed dative form of ja here, and it often marks the person affected or the person something belongs to in a natural, idiomatic way.

So:

• tlak mi je visok literally means something like the blood pressure is high to me
• natural English: my blood pressure is high

Croatian often uses this structure instead of a possessive adjective with body parts, health conditions, and personal states.

Similar examples:

• Ruka me boli. = My arm hurts.
• Glava mi je teška. = My head feels heavy.
• Temperatura mi je visoka. = My temperature is high.

Yes, you can, but tlak mi je visok is usually more natural in everyday Croatian.

Compare:

• tlak mi je visok = the usual, idiomatic way
• moj tlak je visok = understandable, but more emphatic or contrastive

You might use moj tlak if you want to stress my in contrast with someone else’s:

• Njegov tlak je normalan, ali moj tlak je visok. = His blood pressure is normal, but my blood pressure is high.

So both are correct, but tlak mi je visok is the more typical phrasing.

Because mi is a clitic. Croatian clitics usually go in the second position of the clause.

In tlak mi je visok:

• tlak is the first element
• mi comes right after it
• je is also a clitic, so the clitics group together

This second-position behavior is very common in Croatian.

You will often see patterns like:

• Ivan mi je rekao.
• To mi se sviđa.
• Sestra mi je kod kuće.

So the placement of mi is not random; it follows a regular clitic rule.

Because visok is being used as a predicate adjective, after the verb je.

In Croatian:

• visok tlak = high blood pressure
  Here the adjective comes before the noun and has the usual attributive form.

• tlak je visok = the blood pressure is high
  Here the adjective is part of the predicate, so you use visok, not visoki.

Also, visok agrees with tlak, which is:

• masculine
• singular

So visok is the correct form.

Because the sentence describes a general repeated situation or usual result:

• Kad imam previše stresa = whenever / when I have too much stress
• tlak mi je visok = my blood pressure is high

Croatian often uses the present tense for this kind of general truth or repeated condition, just like English can say:

• When I’m under too much stress, my blood pressure is high.

So this is not only about one specific moment; it can describe a pattern.

Yes.

• kad = when
• ako = if

In your sentence, kad suggests that this happens as a regular or expected connection:

• Kad imam previše stresa, tlak mi je visok. = When I have too much stress, my blood pressure is high.

If you said:

• Ako imam previše stresa, tlak mi je visok.

that would sound more like a condition: If I have too much stress, my blood pressure is high. It is not wrong in every context, but kad fits better when you mean a usual pattern.

Yes. Croatian word order is flexible, though some versions are more natural than others.

These are all possible:

• Kad imam previše stresa, tlak mi je visok.
• Tlak mi je visok kad imam previše stresa.
• Kad imam previše stresa, visok mi je tlak.

The first one is probably the most neutral and straightforward.

The choice depends on what you want to emphasize:

• first clause first = sets up the condition first
• visok mi je tlak = puts more focus on high

So Croatian allows variation, but the original sentence is a very natural default.