so what's with the "the" in the hungarian original? is it necessary? Because "I like the girls is wrong, I believe.
Yes, it's necessary. Both "I like girls" (referring to girls in general) and "I like the girls" (referring to a specific group of girls) are translated as "Szeretem a lányokat."
That's not a correct sentence; the indefinite article can never be followed by a plural noun (just like how you wouldn't say "a girls" in English).
"Néhány", just like all other numerals in Hungarian, takes a singular noun, so you would have to say "Szeretek néhány lányt."
I belive in that case you would also have to use the indefinite, i.e."Szeretek egy lányt".
I know this is off topic, but can someone please explain how is the word 'szeretlek' constructed?
Sure, the basic form of the verb is szeret. You add -lek which is a special ending used when the subject of the sentence is the 1st person (I) and the object of the sentence is the 2nd person (you). The -lek ending conveys "I ...(verb)... you" all by itself, and those pronouns do not need to appear in the sentence. It is explained somewhat further in the tips here:
Thanks. Does it means there are endings for cases in which the subject is in 2nd person and the object is in 1st etc? Or is it just the case with -lek?
No, -lek is the only ending which specifies both subject and object.
All other endings only specify a subject and whether there is a definite object or not.
But the object of this sentence is in the 3rd person (lányokat). Why do we use here the -lek suffix?
You don't use it in this sentence.
LukaJović1 explicitly stated that his question was off-topic. Ignore it :)
No. Two reasons. First an object without an article must precede the verb - and the verb must be in the indefinite mood ie "Lányokat szeretek".
But that is not what the English sentence means. The English sentence is a general statement so must take a definite article "a". "Lányokat szeretek" would be "I like any girls".
The English translation is incorrect both here and in the exercise. It should be: "I like the girls."
There is a further problem that this set of exercises has. It contains the definite conjugation even though it has not been covered yet.
This is not a problem if a student is racing through the complete set of exercises and returns to do exercises from levels 2 and on. However, it is a problem if the student is pursuing a deeper mastery of a section, e.g., level 4, before proceeding to the next grammar topic.
In English a general subject often does not have an article. So "I like girls" is acceptable for "I like the girls". The real problem comes when translating from English to Hungarian - "I like girls" MUST be translated as "Szeretem a lányokat".