Don't interfere in what doesn't concern you.（what引导宾语从句）

=Don't interfere in the thing that doesn't concern you.(that引导定语从句）

不要干涉/干预/介入与自己无关的事情。

备注(1)：为融合型关系代词/复合型连接代词引导宾语从句，what=the thing that

备注(2)：interfere 为不及物动词，如果接宾语，需要加介词“in/with”意思“干涉;干预;介入/妨碍;冲突;抵触”

I wish everyone would stop interfering and just leave me alone.

我希望大家都别再来干涉我,让我一个人静一静。

(1)interfere in sth 干涉/干预/介入某事

The UN cannot interfere in the internal affairs of any country. 

联合国不能干涉任何国家的内政。

(2)interfere with sth妨碍/冲突/抵触某事

Drug problems frequently interfered with his work.

吸毒问题频频干扰他的工作。

Alexander wasn't going to let a lack of space interfere with his plans.

亚历山大不会让空间不够的问题妨碍他的计划。

Smoking and drinking interfere with your body's ability to process oxygen. 抽烟与酗酒有碍身体处理氧气的能力。