This is a gGerman car , almost new and (black in color / black-colored).

Proper nouns (like nationalities and names) are capitalised

"black in colour" is a sort of unique grammar only used in this case, it's a little poetic. "black-coloured" is just a standard adjective. You could also go with "black and almost new".

He likes his car very mucha lot and often worries about car thiefves.

"thieves" is the plural of "thief"

"Very much" is something that non-native speakers often overuse, other phrases like "a lot" fit better here.

Doctor Donelli uses his car every single day - he goes to the office on his car, drives to do shopping or visit his friends.

When we use a dash to break up a sentence most people put spaces around either side. Some people omit spaces around an em dash (the long one: —), but that usage is a little old fashioned. (And the em dash is becoming unpopular because AI uses it a lot). Either way, for a dash for a break, it should be the same both sides, if you're going to use spaces, include both spaces.

Often on Sunday, he goes to his parents who live outside of the city.

After allOn top of that, one or two times per year dDoctor Donelli goes travelling oin his car.

"on" his car would mean he was on the roof.

"After all" would imply this was a summation of what's come before, which it isn't.

MIn the morning , when dDoctor Donelli goes to the office , he always leaves his car oin a custodyyvaleted parking.

Assuming by "custody" parking you mean parking where you give your car to someone else and they bring it somewhere, then that's called valeted parking.

If you just mean parking that's not available to everyone, that's just called "private parking"

EIn the evening, when he returns home, he puts his car into the garage.

On Saturday, when he is finally nont working and has a little free time , he checks the engine and checks the tires.

Don't forget to keep up the progressive tense.

In the city where he lives there is a heavy traffic and the streets are small and narrow and because of that there is often a traffic jam.

"traffic" is uncountable, so doesn't take a "a"

On the other hand "a traffic jam" can use "a" because the "jam" is considered countable

When stopped in a traffic jam , dDoctor Donelli listens music or uses telehis phone to spentd time.

"telephone" written out in full is getting a little old fashioned when used to refer to using a phone for any reason other than calling. People might still talk about a telephone when using it to call someone, but otherwise (especially if someone is e.g. browsing the internet on it), people will usually either call it a smartphone or just call it a phone

Sometimes he calls home and says totells his wife to do aprepare lunch, sometimes he calls to the office and says totells his secretary to write a letter or find a document.

"tells" has the connotation of instructing/ordering much more than "says to" does, so is more natural here.

"calls to the office" would mean physically showing up at the office for a brief visit
"call the office" would mean phoning the office

Even if he is stoppped in a traffic jam for some time , he feels good in his car because ithis is a very comfortable car which means hobbit's.

"hobbits" are small, human like people with pointy ears from the lord of the rings franchise.

Maybe you meant "hobbies" but I'm not quite sure how it fits in with your point so I just removed it.

ThisIt is a german car , almost new and black color.

Doctor Donelli uses his car every single day -he goes to the office oin his car, drives it to do shopping or visits his friends.

Often on Sunday he goes to his parents who live out of the city.

After all, one or two times per year doctoDr Donelli goes travelling oin his car.

Morning , when doctoDr Donelli goes to the office , he always leaves his car oin a custodyymonitored car parking.

EIn the evening, when he returns home, he utparks his car into the garage.

Saturday, when he finally he is nont working and has a little free time , he checks the engine and cthecks tires.

When stoppedationary in a traffic jam , doctoDr Donelli listens to music or uses the telephone to spentpass the time.

Sometimes he calls home and says to his wife to domake a lunch, sometimes he calls to the office and says toasks his secretary to write a letter or find a document.

Even if he stopppedis stuck in a traffic jam for some time , he feels good in his car because ithis is a very comfortable car which means hobbit's.

This is a gGerman car ,which is almost new and black color.

Doctor Donelli uses his car every single day -he goes to the office oin his car, drives to dgo shopping, or visits his friends.

After all, one or two times per year doctor Donelli goes travelling oin his car.

MIn the morning , when doctor Donelli goes to the office , he always leaves his car oin a custodyyvalet parking.

EIn the evening, when he returns home, he utparks his car into the garage.

On Saturdays, when he is finally nont working and has a little free time , he checks the engine and checks tires.

In the city where he lives there is a lot of heavy traffic and the streets are small and narrow and because of that there is often a traffic jam.

When stopped in a traffic jam , doctor Donelli listens to music or uses his telephone to spentpass the time.

Sometimes he calls home and says toasks his wife to do amake lunch, s. Sometimes he calls to the office and says toasks his secretary to write a letter or find a document.

Even if he stopppedis stuck in a traffic jam for some time , he feels good in his car because this is a very comfortable car which means hobbit's.

I'm unclear what "means hobbit's" refers to