But as for me

This phrase shows that the writer is changing from speaking about wicked people to talking about himself.

I will walk in integrity

"Walk" here is a metaphor for behavior. AT: "I will behave with integrity" (See: rc://en/ta/man/translate/figs-metaphor)

Here "foot" represents the whole person. AT: "I stand" (See: rc://en/ta/man/translate/figs-synecdoche)

Possible meanings are that "level ground" represents 1) a safe place or 2) right behavior (See: rc://en/ta/man/translate/figs-metaphor)

"when I gather with the people of Israel I will praise you"