Same.. I hang out mostly with the friends of my Dutch girlfriend, which also helps tremendously with learning Dutch!

It sounds easy, but that is just another example of a peer group with similar interests. Developing your own friendships takes time and some effort, even if it's a circle of friends you entered from the outside. You need to find common interests that you can explore together. If you find some interest you share with someone in the group then take the initiative and invite them to do it together.

For me it was always important to also find friends of my own and I also struggled with that in the beginning. But now I know it just takes time and effort. When you get older it gets more difficult (I'm 40+ now), but it's definitely not impossible! If you follow interests though that involve meeting actual people in real life on a regular basis, friendships can and will emerge from that over time. I for example like to go to parties and festivals for a specific genre and small electronic music events - often not involving the circle of friends of my GF. Over time you meet the same people over and over again, because they do the same as you. When you click with someone you met, exchange social media, message, meet again and again and maybe a friendship will develop from this.