This meter also works after a few weeks daily repeated measuring more accurately and quickly displays the value. An oak has not been necessary, the device always showed so far on the exact value of the buffer solutions. I enjoy that.
The manual is in English and German and in addition also contains reports on practical experience with electronic measuring instruments in general, and pH meters in particular.
I highly recommend this unit highly.
It has a wide range of functions, compact yet affordable. From me 5 stars and strong buy recommendation.