Hardtekk is a genre quite popular in Germany. Its know for having not much melodies, being repetitive and using a lot of distortion so that everything sounds a bit cheap. It is also quite popular in combination with German rap.

Speedcore is techno with 400+ bpm and Extratone is everything above 3600 BPM. This is The Rate at which the beats turn into a single tone and you can’t hear the single beats.

Examples for Hardtekk:
www.youtube.com/watch?v=Wqu8LHByWRI
www.youtube.com/watch?v=x-ZTVw2R9wA

Examples for Melodic Extratone:

www.youtube.com/watch?v=-AH4khgBBpY
www.youtube.com/watch?v=8HaK_MR0KXg

Examples for Extratone:

www.youtube.com/watch?v=kkivY3wwQHc (this one is technically Splittercore, but it does has good Extratone elements)
www.youtube.com/watch?v=i85jXEhukz8 (the end is Extratone)

Examples for speedcore in general:

www.youtube.com/watch?v=mOU4WDMchMY (check out the part starting at 4:20 that shit is sick)
www.youtube.com/watch?v=9pRpkbJdqVg