I've bought quite a bit from China over the years, mainly electronics, hardware, or cycling accessories, and much of it via AliExpress. As Paddy says, the quality usually matches the price. The frame linked above is aluminium, so may not be suited to an area where it will be exposed to strong winds. Most companies here would use a steel frame.
Is there any particular reason that you want a glass roof? It will be a little more scratch resistant, but it will be much more liable to breakage. For overhead use, you will need to use laminated safety glass and the fixing points will need to be professionally drilled, be 100% accurate, and allow for movement in the frame so as not to put strain on the glass. Prices won't be much cheaper than poly carbonate. If you want curved glass to fit the above frame, you're looking at a more expensive custom job.
For that size roof, you should be able to pick up 8mm poly-carbonate for around €1000, that will flex to a curved frame and is easily drilled.