In most cases, the meaning of "hendak" differs from "harus" and "mesti". On the other hand, if you use "mesti" then it is as if you're saying "You're obliged to do such and such" or "You must do that" whereas in "harus" it is as if you're saying "You're urged to do such and such.". Nonetheless these two words are sometimes interchangeable. Since "mesti" is a stronger word compared to "harus" therefore both are comparable with "must" (mesti) and "should" or "shall" (harus) respectively. "Hendak" - to use this word you'll have to look at the context. If you say, "Saya hendak pergi ke kedai", that's "I want to go the shop", on the other hand if you were to say "Kita hendaklah bersikap adil" then you'll say "We have to be just" or "We should exercise justice" E.g. Saya HARUS pergi ke sekolah - I (have to go) to school. Saya MESTI siapkan tugasan saya - I (must) complete my assignment. Saya HENDAK melawat rakan - I (want) to meet a friend. Hope this helps and I wish you all the best in learning Malay! Hit me up if you're interested in some casual conversation or improving your Malay. -Wan