"I know myself."
Translation:나는 내 자신을 압니다.
저 is formal and 나 is not formal so combining 저 and 내 in the same sentence is wei4d
In 합쇼체, verbs whose verb stems end in ㄹ drop the ㄹ before the -ㅂ니다. So with 알다, the ㄹ gets dropped from 알 and the conjugation become 압니다. Another example is 살다 (to live) becoming 삽니다.