Hello,
I have added a product to the cart http://prntscr.com/jkzww2 I can view the added product both in the header and in sidebar http://prntscr.com/jkzx5x
Please clarify your problem with the cart. Have you tested on the default theme? What is the result?
What do you mean saying coupon does now work? Have you tested that on the default theme?
As for the language switcher, it could be reset during the incorrect update. You can add it again in your WPML > Languages > Menu language switcher http://prntscr.com/jl004j
Best Regards