There is no magic cure for plastic, battery-operated, digital, water timers that are exposed to weather.Try spraying WD40 on the button.Turn timer upside down and spray WD40 again so debris can work it's way out of timer button.Keep a cover over timer, do not expose to direct hot sun, and do not expose to freezing water or inner plastic valves will break.Buy another timer.Copy following link for Gardena manuals:
http://waterheatertimer.org/How-to-program-Gardena-C1060.htmlCopy following link for various other water timers, Toro, Orbit, Melnor, Raindrip etc in no particular order.
http://waterheatertimer.org/Woods-timers-and-manuals.html#sprinkler If you need further help, I’m available over the phone at
https://www.6ya.com/expert/gene_9f0ef4df2f9897e7