Look first of all if you gonna learn language please stop thinking of this is a translation of your language. . Each language has its unique phrases and structure. So in arabic you can say : 1/ i reached the sixth(year) of my age or /of age / انا بلغت السادسة من عمري أو انا بلغت السادسة من العمر او السادسة 2/my age is seven عمري سبع سنوات Those are i classic arabic But in dialectical arabic like egyptian arabic You can say i have seven years انا عندي سبع سنين Second part of your question is NO .. age is not feminine word it's a muscline And why we put third in fimine form because it's up to " years " which is feminine word So he reached the third year of age هو بلغ السنة الثالثة Year may not been included in this phrase like you see I hope It was clear and if you need anything else don't hesitate to ask me This is my Facebook because i don't enter here too much https://m.facebook.com/khaled.fadl.182?__nodl