A transcript from Turkey comes in a hundred point or five point system. An American application expects an average out of four, and there is no standard conversion between them.
Who does the conversion
Most institutions take the raw transcript and evaluate it with their own table. Some ask for a report from an authorised evaluation body.
In both cases the student does not do the conversion. A four point average calculated by the student is not used in the application and, when calculated wrongly, costs credibility.
Why the school profile matters
An 85 means very different things depending on the school. The school profile document the school sends provides that context: grade distribution, class size, advanced courses offered.
Without that document a transcript is a context free list of numbers. Preparing and sending it is something the school does and the student has to follow up.
How course load is read
Selective institutions look not only at the average but at which courses produced it. A high average from easy courses is not stronger than a slightly lower one from demanding courses.
That raises the value of AP or IB courses appearing on the transcript.
Official submission
The transcript is sent officially by the school. A copy held by the student is not accepted at most institutions.
Some institutions ask for a notarised translation. That detail is on the institution's own page and is read before sending.
For a student at a Turkish school
A transcript from a national curriculum school is unfamiliar to an international reader. That is not a disadvantage but an uncertainty, and what closes it is the school profile together with a standardised test score.
Much of the weight the SAT carries for an international student comes from exactly this: it is the only number that makes different systems comparable.