Does only 9 days dose of 20mg famotidine cause erectile dysfunction? how it cure now?

Doubt it: I have never heard of anyone getting ed from famotadine. If you stop using it it should be out of your system in just a couple of days.

Sorry, but not it...: There are rare instances where impotence has been reported with Famotidine use, but no more frequently than reported with placebo. In fact, the 20mg dose you've taken is a relatively tiny one. Impotence can reflect many problems--hormonal, vascular insufficiency, performance issues, medication & substance-related, etc. A trip to your urologist is your best next step in getting an answer & cure.