try to find my place

No one's perfect. We all mess up now and then and wish we could hit some magical "undo" key. It can help a little bit to remember that most people have been in the situation you're in.
What makes the difference is what you do next.
Use the power of a sincere apology. Apologies can go a long way toward healing hurt or angry feelings. It takes courage to step up and admit what you did was wrong.
Try saying: "What I said the other day was really insensitive of me. I shouldn't have said that. It wasn't fair. I was being judgmental and gossipy — and I don't feel proud of that. I just want to say I'm sorry. I messed up."
The important thing about an apology is sincerity. When we apologize, we need to do so because we feel genuinely sorry about how hurt another person may be. An apology shouldn't be a way to protect our own image or be liked. If an apology is more about ourselves and how we can benefit, it might not seem true.
Another element of a sincere apology is the intention to change. Let the person know you're not going to let it happen again. You could tell your friends, "I'm going to be more aware of what I think and say about people in the future. I'll make an effort to be kinder and more positive about people, and not to talk behind their backs — especially when it's my friends."
Apologizing in person is best. If you can't bring yourself to have a conversation in person, write a note. Whichever way you decide to communicate, be sure that you'd feel comfortable if anything you say is shared with other friends, too.
Hopefully, your friends can accept your apology. But don't be discouraged if it doesn't happen instantly. Some people are quick to forgive. Others may have to think about what you said and need time to get over hurt feelings or anger, or to regain trust. Do your best with the part that's up to you. The rest is up to them.
Forgive yourself, too. We can learn from mistakes. Focus on mending the situation, not replaying it in your head. Being too self-critical can't help you. Neither can wishing the situation away, thinking about what you said over and over, or dwelling on what you could have said instead. Move forward. Focus your energies on trying to make things right and working on your good intentions!