Hi, I am Dave, I will help you with this.
There is currently no shortcut to donwload an image in Chrome based browsers, you would first need to navigate through the web page to select the image and then right click the image, if your touchpad is not working, how are you managing to navigate around the web pages?
The best option if your touchpad is not working correctly would be to go to the support page for your laptop on the Dell website to download and re-install (not update) the version of Chipset drivers and Touchpad drivers they provide for your laptop model.