修好(xiū hǎo) - to fix, to repair successfully; to make peace in Mandarin

修好 (xiū hǎo) is 修 plus the resultative complement 好, and the 好 is doing real work: it says the repair actually succeeded. 我修了两个小时 means you spent two hours on it. 我修好了 means it now works.

Because it is a resultative pair, other things slip between the two halves. 修不好 is cannot be fixed, 修得好 is can be fixed, and 修好了 marks the finished job. That flexibility is why the pattern is worth learning as a unit.

There is a second, formal sense: 修好 as establishing or restoring friendly relations, used of families, neighbours and states. The trap for English speakers is the first sense, though. English says "I repaired it" and leaves success implied. Mandarin does not, so 我修了 without 好 leaves your listener wondering whether the thing works.