Hello Ahmed,
When you meet someone for the first time by making an acquaintance:
"Ich freue mich , dich (Sie) kennen zu lernen."
Otherwise when meeting someone you already know ,a friend or so:
"Schön dich zu treffen."
In a formal way you could also say when meeting someone :
" Guten Tag ( Abend) Sehr angenehm!" = pleased to meet you!
If you writing a formal letter for example you could be more formal saying :
" Sehr erfreut, ihre Bekanntschaft zu machen."