"Jak je to velké?"

Translation: How big is it?

[skywalker735]

Can we change the position into 'jak velké je to?'

[ValaCZE]

yes

[Mumsyx5d]

Why is "how is it big?" Wrong?

[BoneheadBass]

That is a literal translation that is very strange. In English, "How is it big?" would be asking by what means/mechanism something is big, and I don't know if that fits the Czech sentence. Literal translations sometimes work. But here... maybe not so much.