ДАЙТЕ ВІДПОВІДІ - English

Take meaning 3 (the one similar to "Only") and you could easily substitute Just with Only while in the other example Only does not work. Try with this substitution to see if the difference is clear. For any question/doubt or even just to let me know if this worked, feel free to write a comment or an email. Bye!

Hello!
Just and Only are similar but sometimes they are used in a slightly different way.

Let's start from Just. Just has several sets of meanings, here's the main ones with examples:
1. connected with time: e.g. Lucy's just come back. / I've just finished my report.
2. meaning "exactly": e.g. Thank you so much. It's just what I wanted.
3. meaning "only":
e.g. Lucy left after just half an hour. / It costs just a few pence. / We just wanted to make sure everyone was safe.
4. adding emphasis: e.g. I just can't believe what happened! / Just look at the dress she's wearing!
5. adding politeness: e.g. Could I just borrow your pen?