increase - make bigger or more; "The boss finally increased her salary"; "The university increased the number of students it admitted"

prolong, protract, draw out, extend - lengthen in time; cause to be or last longer; "We prolonged our stay"; "She extended her visit by another day"; "The meeting was drawn out until midnight"

elongate, stretch - make long or longer by pulling and stretching; "stretch the fabric"

grow - become larger, greater, or bigger; expand or gain; "The problem grew too large for me"; "Her business grew fast"