We use olyan before an adjective to mean "...as...as...".

Ági olyan okos, mint én. Ági is as smart as I.

Of course we can use nem too, to mean "not as ... as ...":

Ági nem olyan okos nálam. Ági is not as smart as I.

N.B. here, mint or -nál means "as" rather than "than."

See comparative for more details of mint and -nal.