Sredinom tjedna obično radim prekovremeno.

Sredinom is the instrumental singular of sredina (middle).

In this sentence, sredinom + genitive is a common time expression meaning in the middle of or around the middle of something:

• sredinom tjedna = in the middle of the week / midweek
• sredinom mjeseca = in the middle of the month
• sredinom godine = in the middle of the year

So sredinom is not just a random form here; it is part of a fixed and very natural temporal pattern.

Because sredinom is followed by the genitive case.

The dictionary form is tjedan (week), but after sredinom it becomes tjedna:

• tjedan = week
• sredinom tjedna = in the middle of the week

This is something learners often just need to memorize as a pattern:

• sredinom + genitive

Yes, you can, and it is also natural.

• sredinom tjedna = midweek / in the middle of the week
• usred tjedna = in the middle of the week

They are close in meaning, but there can be a slight nuance:

• sredinom tjedna often sounds a bit more neutral and time-related
• usred tjedna can sometimes feel a bit more like right in the middle of the week

In many everyday contexts, both work.

Croatian often leaves out subject pronouns when they are not needed.

The verb radim already tells you the subject is I, because it is the 1st person singular form of raditi.

So:

• radim = I work / I am working
• ja radim = I work with extra emphasis on I

In this sentence, ja is unnecessary unless you want contrast or emphasis.

The infinitive is raditi (to work / to do), and its present-tense forms are:

• radim = I work
• radiš = you work
• radi = he/she/it works
• radimo = we work
• radite = you plural/formal work
• rade = they work

So radim is simply the correct present tense, 1st person singular form.

Because Croatian, like English, often uses the present tense for habitual actions.

This sentence describes a repeated routine:

• obično radim prekovremeno = I usually work overtime

It does not mean only I am working right now. In this context, the present tense means this is what typically happens.

Because the sentence describes a habitual, repeated activity, Croatian normally uses the imperfective verb raditi.

Croatian aspect matters a lot:

• raditi = imperfective, ongoing/repeated/habitual
• a perfective verb would suggest a completed action, which would not fit as well with obično (usually)

So obično radim is natural because it means I usually do/work, not I complete the work once.

Here, prekovremeno functions as an adverb, meaning overtime.

So:

• raditi prekovremeno = to work overtime

It comes from the adjective prekovremen / prekovremeni, but in this sentence it is being used adverbially.

You may also hear related expressions like:

• raditi prekovremeno
• raditi prekovremene sate = to work overtime hours

Yes, Croatian word order is fairly flexible, and obično can move.

The given sentence:

• Sredinom tjedna obično radim prekovremeno.

Other natural possibilities include:

• Obično sredinom tjedna radim prekovremeno.
• Obično radim prekovremeno sredinom tjedna.

The basic meaning stays the same, but the focus can shift slightly depending on what you want to emphasize.

The original version sounds very natural and balanced.

In standard Croatian, tjedan is the normal word for week.

Sedmica exists in some varieties of the language, but it is not the standard everyday Croatian choice in the same way. A learner of Croatian should strongly prefer:

• tjedan = week

So sredinom tjedna is the standard Croatian expression.

Yes, in isolation radim can correspond to either I work or I am working, just like many present-tense verbs in Croatian depend on context.

But because the sentence contains obično (usually), the intended reading is clearly habitual:

• I usually work overtime midweek

So here it is not about one action happening right now.

You negate it by putting ne before the verb:

• Sredinom tjedna obično ne radim prekovremeno.
• Midweek I usually don’t work overtime.

This is the normal Croatian way to negate present-tense verbs:

• radim = I work
• ne radim = I do not work

Yes—there are three very useful patterns here:

1. sredinom + genitive for time expressions

   • sredinom tjedna
   • sredinom mjeseca

2. present tense for habitual actions

   • obično radim = I usually work

3. raditi prekovremeno as a common expression

   • to work overtime

So this sentence is a good model for building many similar ones, such as:

• Sredinom mjeseca obično imam više posla.
• Vikendom obično ne radim prekovremeno.
• Pred kraj tjedna često sam umoran.