I can't use one of keyboard keys

In a non-english language (Persian) when I want to use a special character, I should tap on shift key (⇑) and then use the character. Other way is hold one special key to use the character. In second way, I can use the character, but in first way not. ---------- Real happening: I tap on Shift and ‍ع for using char غ. I do this but instead of غ, char ع is written, but when I hold ع, char غ is writen and I want it. ---------- Problem solved: I disable suggestion system and problem solved. I use android 6 and system's default keyboard. Excuse me if I describe badly :(