no one is alone if ,someone has left you that means they had a different path then your's. but it doesn't means you won't have new friends in future believe in the process of life , if something ends another thing starts .
you can start actively socializing. like talk to people in your workplace, or college or school whatever. try to know them better. talk about random things. learn how too make friends
you can learn how to make friends from many books
many people here were saying to make a discord group so i made it. if you want to join it and be friends with us online. here's the link:.https://discord.gg/GXfvPG3PeX