"... speak about girls" also looks OK for me.
Just how is "These boys talk about girls often" wrong?!
That's what I'm saying
"A lot" overlaps in meaning with "many" ("a lot of things"), "much" ("a lot of stuff") and "often" ("to do something a lot"), but it's more casual than those three.
Is девочках in prepositional or accusative case?
"These boys often speak about girls." Must be acceptable
Duolingo marked мальчики as a word I'd never seen before and I just find that hard to believe.
"these boys talk about girls a lot" is wrong... That's definitely a better translation, no one uses "often" in this way
Yes they do.
I think the given translation is fine and is trying to convey the frequency of the topic rather than how much of their conversation is about girls. Your sentence could be acceptable but also understood as the latter.