Wiring a Smart Wall Switch
Don't hook stuff like this to mains wiring.  This product is not listed by BSI, TUV, CSA, UL or any reputable testing lab.  As such it may not be legal to install.  

A quick peruse of the brand says that they don't even bother faking a CE stamp, CE being not a testing lab at all, but a mere promise of self-certification, that is meaningless unless the seller is a bricks-and-mortar manufacturer or importer with substantial physical presence in the EU.  If Siemens builds it in Germany, CE means something. If Siemens imports it to their warehouse in Rotterdam and then ships pallets to Wickes, then CE means something because Siemens is the importer. Anything having to do with Alibaba, Banggood, eBay, or Amazon Marketplace, they are doing that to evade safety regs: you're the importer. 

So no, leave those products behind, unless they run on batteries.