When you do not want to use DHCP and/or want NetworkManager to ignore some interface that you want to manage manually, just provide a configuration via
/etc/network/interfaces. The interface will then be ignored by NetworkManager. See
$ man interfaces
for further info on how to configure interfaces manually. This is a template file (snippet) that configures the interface
iface eth0 inet static
Obviously you need to change the IP addresses. Note that the last line is evaluated by
resolconf (it's a package/program, I don't mean the
resolv.conf file), when and only when the interface is brought up successfully. You can check if the interface is up with
/sbin/ifconfig. That should output the keyword
UP and the IP somewhere.
gateway in the above snippet denotes the IP of your router. Check if this ip appears in your route with the command
route -n. Then ping your router. If that works, then you could ping 188.8.131.52. If that works check if the DNS correctly appears in the
/etc/resolv.conf file. If it does, then check if you can resolve DNS names. In that order. If something in betweens fails, it is not a problem with your DNS.
If you're not able to get this straight using
/etc/network/interfaces (package ifupdown) and want to know how to bring up an interface with basic commands, drop a comment.
Then you need to investigate how the trouble started in the first place. You've learnt already that you first need to clarify that your machine is able to ping 184.108.40.206 before you conclude to an error at resolving DNS though that server. If all that works fine, but the resolver entry just doesn't get tranfered correctly from
/etc/resolv.conf then continue your research at the documentation of the package
Do not deinstall your dhcp software, when you depend on the internet connection and have few experiences on how to configure an interface manually. There are a lot of high level packages involved with bringing up an interface, namely network-manager, ifupdown and resolvconf and others. Which one does what is not obvious. ;)