Answer
Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- Beard is a great Sunnah. You should try to keep it. However, it is not integral to one’s faith. So, shaving a beard does not take one out of the fold of Islam.
2- If you shave your patchy beard intending to make it grow better, that is not something wrong with that.
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
Beard is a great Sunnah. You should try to keep it. However, it is not integral to one’s faith. So, shaving a beard does not take one out of the fold of Islam.
Therefore, if you shave your patchy beard intending to make it grow better, that is not something objectionable.
Islam teaches us to keep our hair and beard neat and tidy and well-groomed as best as we can.
Sheikh Muhammad al-Ghazali said, “Ugliness is not the Sunnah; beauty is!”
So, I do not see anything wrong if you shave your patchy beard to help it grow better.
Almighty Allah knows best.