After app installation product variants do not show up

[Godapqngonyte]

Recently we installed a "pify form builder" app to our shopify store (modular theme). And we are experiencing some serious bugs like - our product variants do not show up and all products cannot be purchased because it always show "we are out of stock message. Then there is even our mobile menu that stop to work. Can somebody help? I haven't tried yet to uninstall the app, since we are already using this form, but there are so many things that we tried to fix it.

https://www.italala.lt/collections/kavos-pupeles/products/ethiopia-nifas-lafto-250-gr