tl;dr: I'd advise to go over every single paragraph, sentence, and word and question yourself if it is essential (hint: probably its not - sometimes hard to accept, but true).
Mathilde2211 wrote:In my opinion everything that i said is really important, [...]
The first step is to accept, that this is probably not the case. It's more likely that while it's all relevant, not all is (that) important (at least not to the same degree).
- Let go of what you wrote so far. Keep a copy, but be ready to tear apart the nicest formulations you found, because it might enable the following points.
- Merge things where possible. Remove unnecessary clutter in between (pretty words and extensive formulations).
- The letter shouldn't read like a bullet point list, but don't make a long story out of it either. Keep the bare minimum of every paragraph, such that every sentence and every word becomes essential (words like "very" are unnecessary filling clutter in most cases).
- If you are still over the limit: carefully consider which of the points you discuss are the most essential and which other (although relevant) will have the least impact on your application (and yes...there is no universal answer to what those are)
The useful outcome of the above (especially point two) is that to achieve all of this, you need to ensure that each paragraph of your application carries a specific and clear message. No paragraph will say the same things as another paragraph. While one paragraph can/should/might lead into the next, they should stand on their own (mutually exclusive information).
Finally, consider that your cv/application form also contains lots of information, so a clear, well-written, and expressive letter is way more important than an overly long exhaustive one.