We have got a new connection from a local ISP provider, the provider supplied a router and other few devices, then he has configured the device with a password, but he does not allow us to reset or change the password for own. means we are unable to configure anything from our side, Is this good secure for our personal data?
It means that your ISP provider can basically control your network. Change DHCP ranges, control port forwarding etc.
In a business situation, with sufficient contractual assurances, this might be possible. After all, some companies even outsource their complete IT.
In a personal situation, I would take a small SoHo router and connect only the WAN port to the ISP provider's router.
No it is not secure because you cannot access the configuration on the device, it could be a weak password with remote management enabled. Also, how can you do firmware updates without administrative access? I recommend buying your own router and setting it up. Also if you don't want to buy your own router, there should be a small round hole with a button inside of it on the back or bottom of the router which allows you to factory reset the device. Using a small needle or wire you can depress this button while the device is turned on, it will reset and you can search online for the default credentials and configure the device yourself with your own password.
Probably not secure, but I would say there's not enough information to answer this question.
You inherit whatever level of security they provide. If they offer any kind of threat-based protection, that's a plus. If they manage firmware updates to prevent or stop attacks like VPNFilter, that's a plus.
On the other hand, if they use a common admin password across all devices, fail to patch them, and deploy an insecure configuration then that's a huge problem.
So the question is: What do they offer? Are they good enough to deliver that?