I would like to ask about the correct use of "relevant". Dictionaries say that the term "relevant" is follow by "to". However, I know some people (not native speakers) who prefer to use "relevant for". For example: "this is relevant for the purpose of...". Should'nt it be "relevant to the purpose of..."?
The right construction is, as you believe, relevant to.
When describing who something is relevent to, I would use relevant to. You can think of this construction as relevant to + person or pronoun
A sentence using this would be Where he goes at night is not relevant to me.
When describing what something is relevant to, the correct construction is still, relevant to. So, you might hear The statistics are relevant to the report..
In some cases, when describing what something is relevant to, some people use the construction relevant for, which can sometimes work (as in the case Biology is relevant for the development of new medicines.). Relevant for does work as a phrase sometimes, but most of the time, it doesn't read as well.
My advice would be to keep using relevant to, like the dictionary suggests.