Translation:Did you see an ordinary chair anywhere?
"Have you seen a usual chair anywhere?" sounds kind of weird. I think English doesn't commonly put an indefinite article before the word "usual" for some reason.
In British English, we would probably say "Have you seen an ordinary chair anywhere?" However, "Where is my usual chair?" and "Where is the usual chair?" sound fine. Because "usual" implies one particular chair, we need to use a possessive or a definite article. The indefinite article "a/an", which does not refer to a particular chair, but to chairs in general, (possibly restricted to "green chairs" or "ordinary chairs"),sounds odd here.
We actually would use the indefinite article here. It sounds weird because "usual" is an unusual word to use in this context.
"Did you saw" is not correct grammar. It must be "did you see" (or "have you seen"). Simple past tense verbs are never used in questions in English.
I keep writing "the usual" instead of "an ordinary" for обычный/ая/etc.. What would be the translation of "the usual chair" here?