Yep. If the teacher you are talking about is male, then معلّم (mu3allim).
if the teacher you are talking about is female then معلّمة (mu3allimah).
Your-male-teacher: معلّمك (mu3allimuka)
Your-female-teacher: معلّمتك (mu3allimatuka)
If you are talking TO a female and not a male then the suffix -ka would change to -ki in the previous examples.
Your-male-teacher: معلّمك (mu3allimuka) Your-female-teacher: معلّمتك (mu3allimatuka) That is the same in Hebrew. So I have no problem with understanding that. My problem is with: If you are talking TO a female and not a male then the suffix -ka would change to -ki in the previous examples. I don't see the suffixes, I think;) Do I only hear those?
Actually yes. It is a short vowel placed either on top of ـكَ (-ka) for a male, or ـكِ (-ki) for a female. However, since in regular day-to-day writings we don't use diacritics, we just know how to read it by context. Specially that in the sentence above, the speech is dedicated to Samia which is a female's name, hence, "your" must be a feminine one and (-ki) is to be used.
Bonus: some people, Arabs that is, still write it wrong as ـكي - and this is wrong. This is (kee) and not (ki) and does not fit here and has no meaning in this context.
But we were taught in the Tips that possessive ending addressed to a male are -ak, and to a female, -tik. Now suddenly everybody is adding a diacritic to indicate and extra -i or -a. But that contradicts the Tips. Are the Tips simply wrong? Or do they refer to a particular dialect?
They mentioned that in the hints?
No wonder. The thing you mentioned is true in colloquial speech (dialect that is) in Egypt and the Levant. Not standard Arabic.
Besides, the (-tik) part is also wrong because this would be true ONLY if the word does indeed end with Ta Marbúta ة. Otherwise, it should be (-ik). In colloquial that is.
What happened here is that in colloquial or dialects, the moved the vowels from the end of the suffix, and put it at the back of the consonant; So, (-ka) for the male, becamse (-ak) and (-ki) for the female becamse (-ik).
This kind of confirms my theory about DUolingo's Arabic course, and that is they want people to learn some kind of a "traveler's Arabic"; a mixture of dialects and standard Arabic with reduced emphasis on grammar.
Well, for non-Arabs learning Arabic, I really don't have much resources, specially when it comes to grammar and structure. For sounds, I usually advice people to check Youtube as some Arabs and non-Arabs do produce videos on pronouncing some sounds that seem weird to learners. Everything else is based on my own language as a native who learned it in school, and when I hit a dead end I'd usually search about the topic online (in Arabic) to see if I can find a quick brief answer. Sometimes I do even ask people (family and their friends) to see for any issue that I can't resolve; but this kind of an advanced case.
So, for non-Arabs I don't have much really, no more than those "travelers' books" that teach travelers some dialects of Arabic mostly and not standard Arabic. To what I see, it seems that standard Arabic in the West (and East for that matter) is taught and educated about in specialized institutions (e.g. university or college).
However, maybe some non-Arabs here do have resources for standard Arabic that they know of. Maybe you should post your question in the forum of the Arabic language here. Hopefully you'll get an answer soon :)