Suggestions needed for duas for my dad

Please bro do not take me wrong or anythiing, im merely asking this to increase my own knowledge. For the sake of learning more from you, will you explain how reading a certain arabic words for such many times, as instructed ( placing your hand on heart, reciting dua in a glass of water and drinking it, vice versa ) can actually make any difference? Du’a is what comes out from your heart genuinely, without having to worry about if one is reciting dua with the correct pronunciation etc.. in my opinion , one is free to do dua in whatsoever language s/he feel.. it is not limited to any specific words.