You can install the web app. By using chrome browser you can add Duolingo we app to your home screen; I think its better than the native app, but it will drain your battery.
Why "erkekler" means "the guys" not "the boys"? "The boys" is incorrect, don't know why :(
You are wrong. The word "man" generally refers to the word "adam". The word "male" refers to the word "erkek." The word "boy" refers to the word "oğlan". We sometimes say "erkek" for the word "man" depending on the context. But we don't say "boy" for the word "erkek". However, we can say "erkek çocuk" for the word "boy", which actually refers to the word "oğlan" again.
An apple is one apple. But here is ment the men that are eating generally apple. Isn't it? Why do you think, that you need an article in every time?
Apples are countable; we usually talk about one apple or two apples or many apples.
If people like to eat apples generally, we would usually use the plural (without article) rather than speaking about "eating apple" the way we would with a mass noun such as "eating soup" or "eating mashed potato".
What is the difference between 'erkekler elmayı yer' and 'erkekler elmayı yerler'
The sound is off! Even my Turkish partner couldn't understand it. Only when i told him what it was supposed to say he got it but he said you wouldn't combine the first two words like that when speaking.
Nothing to fix - Turkish doesn't use indefinite plurals on objects - see https://www.duolingo.com/comment/7736911 .
So "The men eat apples" is "Erkekler (plural, because it's subject) elma (singular, because it's an indefinite plural object) yer".
"The men eat the apples" would be "Erkekler elmaları yer", with plural (and accusative case ending).
for Erkekler elma yer you have the guys eat an apple. Eekekler is all of a sudden "guys"?