1.3 HDMI to 2.0b GPU's port?
yes
How many Hertz supports this HDMI 1.3 cable?
That answer depends on the resolution you use/select.
4k = 30Hz
1440 = 60Hz
1080 = 120Hz
"And is it worth to buy 2.0b cable while i have 1.3 cable"
No, because your cable is more capable than your monitor.
And for the other people that answered, perhaps you should do more reading...
"HDMI 1.3 defines two cable categories: Category 1-certified cables, which have been tested at 74.5 MHz (which would include resolutions such as 720p60 and 1080i60), and Category 2-certified cables, which have been tested at 340 MHz (which would include resolutions such as 1080p60 and 2160p30)."
"As of the HDMI 1.4 specification, the following cable types are defined for HDMI in general:[75][76]
Standard HDMI Cable – up to 1080i and 720p
Standard HDMI Cable with Ethernet
Standard Automotive HDMI Cable
High Speed HDMI Cable – 1080p, 4K 30 Hz, 3D and deep color
High Speed HDMI Cable with Ethernet"
"A third category of cable was introduced in October 2015 to certify that cables work at the 18 Gbit/s maximum bandwidth of the HDMI 2.0 specification.[77] This category tests cables at 600 MHz (2160p60 resolution), certifying them as Premium High Speed. In addition to expanding the set of cable testing requirements, the certification program introduces an EMI test to ensure cables minimize interference with wireless signals. These cables are marked with an anti-counterfeiting authentication label and are defined as:[78]
Premium High Speed HDMI Cable – 4K 60 Hz, Rec. 2020, and HDR
Premium High Speed HDMI Cable with Ethernet"
Unfortunately not all HDMI cables were created equal.