Frâna am verificat-o ieri, dar diseară las bicicleta tot în parcare.

This is a case of fronting or topicalization.

The more neutral order would be:

• Am verificat frâna ieri.

But Frâna am verificat-o ieri puts frâna first to highlight it, roughly like:

• As for the brake, I checked it yesterday.
• The brake, I checked it yesterday.

Romanian allows this kind of word order much more freely than English does.

Yes, in a way it does, and that is normal in Romanian.

The -o is an unstressed direct-object pronoun meaning it. When a definite direct object is moved to the front, Romanian very often uses a matching clitic pronoun as well. This is called clitic doubling.

So:

• Frâna = the brake
• o = it

Together:

• Frâna am verificat-o = literally The brake, I checked it

In English, that sounds repetitive unless used for special emphasis, but in Romanian it is a standard structure.

The hyphen links the past participle verificat to the unstressed pronoun o.

So:

• am verificat = I checked / I have checked
• am verificat-o = I checked it

Romanian often attaches short object pronouns to the participle with a hyphen in this kind of structure.

It is the perfectul compus, the most common past tense in everyday Romanian.

It is formed with:

• the auxiliary a avea in the present
• • the past participle

Here:

• am = I have
• verificat = checked

So am verificat literally looks like I have checked, but in normal English it often translates simply as I checked.

Because frâna is the definite form: the brake.

• frână = a brake / brake
• frâna = the brake

Romanian usually puts the definite article at the end of the noun, not before it as English does.

So compare:

• bicicletă = a bicycle
• bicicleta = the bicycle

Diseară means this evening or tonight.

It is a time adverb, and it is very common in everyday speech.

Examples:

• Vin diseară. = I’m coming tonight.
• Ne vedem diseară. = We’ll see each other this evening.

In your sentence, dar diseară means but tonight / but this evening.

Romanian, like English, can use the present tense for a planned or expected future action when the time is already clear.

So:

• diseară las bicicleta... = literally tonight I leave the bicycle...
• natural English: tonight I’m leaving the bicycle... or tonight I’ll leave the bicycle...

Because diseară already shows future time, Romanian does not need an explicit future form here.

Because the object is in its normal place after the verb, so no clitic is necessary.

Compare:

• Am verificat bicicleta ieri. = normal order, no pronoun needed
• Bicicleta am verificat-o ieri. = object moved to the front, so the clitic -o is normally used

In the second clause, bicicleta stays after las, so the sentence can simply be:

• las bicicleta

No extra o is required.

No. Here tot does not mean everything.

In this sentence, tot means something like:

• still
• all the same
• again in the same place

So:

• las bicicleta tot în parcare = I’m still leaving the bike in the parking lot / I’m leaving the bike in the parking lot again anyway

It suggests that despite checking the brake, the final decision has not changed.

Romanian tot has several uses, so context matters a lot.

Dar means but.

It introduces a contrast between the two ideas:

• Frâna am verificat-o ieri = one thing was done yesterday
• dar diseară las bicicleta tot în parcare = even so, tonight the bike is still being left in the parking lot

So dar marks the shift from one fact to a contrasting result or decision.

În parcare literally means in a parking lot / in the parking area, but in real usage it can also be understood as in the parking lot if the place is already clear from context.

Romanian often uses a bare noun after a preposition in location expressions more naturally than English does.

So:

• în parcare = in the parking lot / in the parking area
• în parcarea... would usually need something after it, such as:
  • în parcarea blocului = in the building’s parking lot

A fully definite standalone form would be în parcarea respectivă or something similarly specified. In everyday speech, though, în parcare is very natural.

Yes. A more neutral version would be:

• Am verificat frâna ieri, dar diseară las bicicleta tot în parcare.

This version keeps the direct object after the verb and sounds less contrastive or emphatic.

The original sentence is not wrong at all; it just gives extra prominence to frâna.