Ich helfe im Repair-Café mit.

Because the verb here is the separable verb mithelfen, which means to help out.

In a main clause, the conjugated part goes in the usual verb position, and the prefix moves to the end:

• Ich helfe ... mit.

So:

• helfen = I help
• mithelfen = I help out / I join in helping

In a subordinate clause, the two parts stay together:

• ..., weil ich im Repair-Café mithelfe.

Yes, slightly.

• helfen = to help
• mithelfen = to help out, to lend a hand, to help as part of a group or activity

So Ich helfe im Repair-Café mit suggests that the speaker is taking part in the repair café’s work, not just helping one specific person once.

im is a contraction of in dem.

So:

• im Repair-Café = in dem Repair-Café

German often contracts preposition + article this way:

• im = in dem
• am = an dem
• zum = zu dem

Because this sentence describes a location, not movement into a place.

• im = in dem → dative → location
• ins = in das → accusative → movement/direction

Compare:

• Ich helfe im Repair-Café mit. = I help out at/in the repair café.
• Ich gehe ins Repair-Café. = I go into/to the repair café.

A very common German pattern is:

• where? → dative
• where to? → accusative

Because prepositions do not match one-to-one between German and English.

German often uses in for being inside a place or participating in something happening there, while natural English may use at.

So although im Repair-Café is literally in the repair café, the most natural English translation is often at the repair café.

It is das Repair-Café.

That is why the sentence has:

• im = in dem

since dem is the dative form of das.

This follows the gender of das Café.

German nouns are capitalized, so Repair-Café starts with capital letters.

The hyphen is common because this is a mixed compound:

• Repair from English
• Café used in German

German often uses hyphens in compounds, especially when foreign words are involved, to make the word easier to read.

With helfen, you use the dative case.

Examples:

• Ich helfe den Besuchern. = I help the visitors.
• Ich helfe meiner Nachbarin. = I help my neighbor.

So not accusative, but dative.

With mithelfen, you often do not mention a direct person at all, because the idea is more general: to help out.

Because mithelfen can stand on its own.

The sentence is not focused on who is being helped, but on the activity: the speaker is participating and helping out there.

So Ich helfe im Repair-Café mit is complete and natural.

If you want to add more detail, you can, for example:

• Ich helfe den Leuten im Repair-Café.
• Ich helfe im Repair-Café bei Reparaturen mit.

Because German main clauses normally follow the verb-second rule.

In this sentence:

• Ich = first element
• helfe = finite verb in second position

That gives:

• Ich helfe im Repair-Café mit.

You can move another element to the front for emphasis, but the verb still stays second:

• Im Repair-Café helfe ich mit.

Yes.

The German present tense often covers both:

• a habitual action
• an action happening now
• a near-future action, depending on context

So Ich helfe im Repair-Café mit could mean:

• I help out there regularly.
• I’m helping out there now.

Context tells you which meaning is intended.

In a subordinate clause, the verb goes to the end, and the separable prefix stays attached.

Main clause:

• Ich helfe im Repair-Café mit.

Subordinate clause:

• ..., weil ich im Repair-Café mithelfe.

This is a very important pattern with separable verbs:

• main clause: split
• subordinate clause: not split