All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Regarding the beard, you are obligated religiously to let it grow, and as for the mustache, you are required to shave it or shorten it. The Prophet said in a hadeeth, “Trim the mustaches and let the beard grow.” [Al-Bukhari and Muslim] In another wording, “Do the opposite of what the Magians do: cut the moustaches short and let the beards grow.” [Muslim]
The meaning of letting the beard grow is to leave it and to retain its hair and grow it, and not to cut it like a mustache.
As for the mustache, you have a choice between trimming it, removing what is growing past the lips, or shaving it all. There are scholars who hold the view in favor of either way, although the fatwa we adopt is that shortening the mustache is preferred.
We advise you, son, while you are young, to fear Allah The Almighty, accompany the righteous, be keen on seeking knowledge and to stay away from sins as much as you can, and do not blacken your register with them, as youth is the most important stage of life. The servant will be asked about it on the Day of Resurrection, as in the hadith, “The feet of the son of Adam shall not move from before his Lord on the Day of Judgement until he is asked about five things: About his life and what he did with it, about his youth and what he wore it out in, about his wealth and how he earned it and spent it upon, and what he did with what he knew.” [ At-Tirmidhi].
Allah knows best.