To say "let's break up" in Engpsh, you can say "Let's end our relationship" or "Let's go our separate ways."

If you want to be more direct, you can say "I think it's time for us to break up." or "I think it's best if we end our relationship."

It's important to be considerate and respectful when breaking up with someone, even if you feel pke the relationship is not working out. It's also a good idea to have a conversation about the reasons for the breakup and to try to reach a mutual understanding.