What kind of sentence can be used with that expression?
Seems it was used in Harry Potter. Not that I read it or watched it though.
Why does mlada sometimes mean "young" and sometimes "small"?
mladá - young
malá - small
These are different words.
Did I hear that recording correctly? Did the voice not pronounce the "l" in "mladá"? If so, why is that?
The female voice pronounces the /l/ very quietly. I can hear there but just barely. Bear in mind that the audio is not a recording, it's a TTS (text-to-speech) software, an artificial voice that is far from perfect.
Laska is love? Like the feeling? In Poland its a young pretty girl :v
It's love, like the feeling (miłość in Polish). I thought everybody in Poland knows the Czech pop song "Láska nebeská" ;)
It can also refer to a person that you love, regardless of gender.