Hi ,
I wanted to ask about the size of the flyer ? A4 is good ?

Hi there,

good question! :-)

No A4 is too big. Size should be like a postcard (long version, a third of A4)... unfortunately I don't know the right size name... do you know what I mean?

does the flyer have multiple pages?

2 pages: front + back, that's it! Like a postcard

This is DL size 210 mm x 99 mm

okay thank you!
and with the DL sizing, would you like it vertical?

Right!! That's the one!

yes, vertical. :-)

Could you give me feedback on my design? Do you prefer less contrasting or vibrant colors?
Thank you!

Less contrasting or vibrant color.... good question... the green is a must. I like white or grey in combination to the green.