Could usage of public VPN before TOR be more dangerous than only TOR ? With public VPN we hide from ISP that we are using TOR, but VPN know our IP and that we use TOR. Could VPN use some scripts that deanonymize TOR ?
With public VPN we hide from ISP that we are using TOR
If an ISP carefully observed VPN traffic, it could discern that you were using Tor over the VPN. It might provide plausible cover to a casual obvserver but likely wouldn't stand up to scrutiny. The VPN may encrypt the traffic, but packet timings and other artifacts of the traffic being sent across the VPN would still be possible to discern (with closer technical inspection) and VPNs make no attempt to obfuscate them.
Could VPN use some scripts that deanonymize TOR?
Not on it's own, no. It sees as much as your ISP does however VPNs could act as a choke point into the network, if many people used some VPN to connect to Tor over then that VPN gets to see a lot of peoples Tor entry traffic and knows who those people are, if had a collaborating evil exit node then it could make you more vulnerable to correlation attacks and as noted, the ISP too could probably act in this position, with or without a VPN.
Could usage of public VPN before TOR be more dangerous than only TOR ?
Potentially. Using a VPN can increase risk since it exposes your traffic to more parties that it ever needs be exposed to, providing more positions where your traffic could be observed from than are needed.
It depends who's looking, what they're looking for and how hard they're looking for it.