How do you use further in a sentence?

(The adverb further means "to a greater extent" or additional - for a distance, use "farther")

"John was further in debt than his wife knew."

"The product needs further testing to improve its operation."

"Upon further review, the decision on the field has been confirmed."

"Investigators discovered a further case of fraud in the election."

(verb use - "advance")

"He used the crisis to further his own career."