You can say the supplication which prophet Musa alaihi salam said:
Rabb-ishrah ii sadri, wa yassir li ‘amri, Wah-lul ‘uqdatam-mil-li-saani, Yaf-qahuu qawlii
O my Lord! Expand me my breast; Ease my task for me; And remove the impediment from my speech, so they may understand what I say
[Surah Ta-Ha; 20:25-28]