[H@ns]

Hi Donkere Sint,

I have a few recommendations regarding your letter.

Dear Ms Heike Hann

Do you know if she's married? If not, you should use "Mss".

My interest goes to the opening for technical consultant that one of you’re employees, Mr Hendricus Janssen offert me. Willingly I present myself for this opening.

you're must be your
offert muste be offered

I gained a diploma car techniques which I upgraded with a specialisation diesel and LPG techniques.

You specialize in diesel (...)

Dutch, English, French, Arab are no difficulty.
Don't forget the "and" between French and Arab. Also this sentence doesn't really shine off its greatness in English. To be honest this sentence looks like its translated directly from a Dutch one "Deze talen zijn geen moeilijkheid". Try a different sentence here.

I have been improving the last 4 years with courses from GM academy and received gold label this is a statute that GM academy gives for my knowledge.

Have you been improving cars? Or your carreer? Or maybe yourself? You should specify this. Shouldn't it be "the GM academy" and "a gold label"? Don't forget the comma between "label" and "this". Also, "statute" means "richtlijn/aanwijzing". I don't think this word really applies in this sentence.

Weekly I read GM updates and also do GM none obligatory courses.

This sentence should be "I read GM Updates weekly and also do GM nonobligatory courses".

To maintain successful results your company exist of a team that is up-to-date, educated and pasionated.

"Pasionated" should be passionated

I am convinced that I fit in such team.

It's such a team.

I have team spirit, wide experience, service specific attitude, flexible, professional and immune to stress.

team spirit must be teamspirit
'flexible', 'professional' and 'immune to stress' are not things you have, but things you can do. This sentence should be "I have teamspirit, wide experience, service specific attitude and I am flexible, professional and immune to stress".

As technical consultant I could be a valuable contribution to your company.

I'd choose for "would" instead of "could", this shows off your self-confidence

Interested in this captivating oppertunety I hope we meet personally so I can convince you from my capacities

As said by Not-Registered, "oppertunety" must be opportunity.
Also, you don't "convince from something". It's better to use "about"

I hope this helps!