In arabic there is no vowels We have 3 diacritics They seem to be vowel but they are not The first on is فتحة its like this َ it is put on the top of the letter n its pronounced like schwa , the second diacritic is الضمة ُ its pronounced like this sound short /u/ , the final one is كسرة ِ its put under the letter its pronounced as this sound /I/ So marhaba we pronounce as this depending on these diacritics مَرحَبا I hope that u get it ^^