Otkako smo došli u sobu za bijeg, tražimo nevidljivu tintu.

Otkako means since or ever since. It introduces the point in time when something started.

So Otkako smo došli u sobu za bijeg means Ever since we came/arrived in the escape room.

It tells you that the action in the main clause started at that moment and is still relevant now.

Because the two actions are viewed differently:

• smo došli = a completed event in the past
• tražimo = an action that started then and is still going on

Croatian often uses the present tense in the main clause after otkako when English would use something like have been looking.

So the structure is basically:

• Since we arrived, we are looking for... in Croatian grammar
• but in natural English, often Since we arrived, we’ve been looking for...

Smo došli is the perfect tense.

It is made of:

• smo = the auxiliary verb to be for we
• došli = the past participle of doći = to come / to arrive

So smo došli means we came or we arrived.

In Croatian, the past participle agrees with the gender and number of the subject.

With we, the forms are:

• došli = masculine plural, or a mixed-gender group, or unspecified gender
• došle = all-female group

So if the speakers are not all female, došli is the normal/default form.

Because Croatian uses different cases depending on whether you mean movement toward/into a place or location in a place.

• u + accusative = movement into
• u + locative = being in

Here, u sobu shows motion: we came into the room.

Compare:

• Došli smo u sobu. = We came into the room.
• Mi smo u sobi. = We are in the room.

Nevidljivu tintu is in the accusative singular feminine because it is the direct object of tražimo.

Base form:

• nevidljiva tinta

Accusative form:

• nevidljivu tintu

Both words change because adjectives in Croatian must agree with the noun in:

• gender
• number
• case

So:

• tinta → tintu
• nevidljiva → nevidljivu

Because Croatian can use the present tense for an action that began in the past and continues into the present, especially after words like otkako.

So tražimo does not just mean a simple present we look for in the English sense. In this kind of sentence, it often corresponds to:

• we have been looking for
• we’ve been searching for

This is a very common difference between Croatian and English.

They show a very natural aspect contrast:

• doći is perfective: it describes a single completed event, the arrival
• tražiti is imperfective: it describes an ongoing process, the searching

That fits the meaning perfectly:

• first, the arrival happened
• after that, the search has been continuing

This is one of the main things Croatian aspect is used for: completed event vs ongoing activity.

Yes, it is understandable and natural enough. Literally it means room for escape.

That said, in everyday use, many speakers also simply say escape room. Borrowed English terms are quite common.

So soba za bijeg is a good Croatian expression, but you may also hear the English form in real life.

Often yes.

Both otkako and od kada can mean since in time expressions. Otkako is a compact one-word conjunction, and od kada is a more transparent two-word version.

You may also hear the shorter form otkad.

So these are all possible in many contexts:

• Otkako smo došli...
• Otkad smo došli...
• Od kada smo došli...

In this sentence, otkako sounds very natural.

Because Otkako smo došli u sobu za bijeg is a subordinate clause, and it comes before the main clause.

Croatian normally separates this kind of clause with a comma:

• Otkako smo došli u sobu za bijeg, tražimo nevidljivu tintu.

That comma is standard and expected.

Yes. Croatian word order is fairly flexible, but the version you have is the most neutral and natural.

One important detail is that the clitic smo tends to stand near the beginning of its clause, usually in second position:

• Otkako smo došli u sobu za bijeg...

You can change word order for emphasis, but beginners are safest using the sentence as given. It sounds clear and natural.