Noting this new phrase I’d never heard before.
Limar means to rub something with a lima – a file. I mean one of those scrapey things you use in metalwork class or in the nail bar.
Aresta can have a few different meanings, but in this context, it’s a pointy, sticky-out bit the corner or the edge of something.
So the general idea is you’re rubbing off the rough edges, polishing something or perfecting it.
According to Ciberdúvidas, it can also mean to conciliate a difficult person. That’s a very different idea, but you can see how they both make sense of you’re thinking of smoothing things over with someone.
Luso 