Local network depends on Internet connection

I have a very weird problem with our router. 

 

I have one server, that is directly connected to the router via Ethernet and runs a program, that I can access from inside of the local network. Normally it should not be dependant of our internet connection, however if our internet is slow, also the local network is slow. And if our internet is gone (since we didn´t manage to pay the bill) the Local Network also stops working.

Our router is a TP-Link Wireless N4G LTE Router Model No. TL-MR6400 with LTE network. It contains a SIM-card that connects us to the local mobile network (which is our connection to the internet). 

The problem is appearing independent of the computer I am using. All computers in the Local Network as well as the Server are HPs of different models. All computers except the Server are connected via WLAN.

 

The servers internal IP-adress is 192.168.1.10/

I have little knowledge in routing tables, but I wasn´t able to find a reason for the local network somehow going over the internet. 

 

This is the routing table of the router (System Routing Table, the Static Routing List is empty):

 

 

 

*————*——————————*——————–*———————*——————-*

 

| ID          | Destination Network | Subnet Mask | Gateway          | Interface       |

 

*————*——————————*——————–*———————*——————-*

 

| 1            | 192.168.1.0                | 255.255.255.0 | 0.0.0.0             | LAN & WLAN | 

 

| 2            | 10.37.191.0                | 255.255.255.0 | 0.0.0.0             | WAN              |

 

| 3            | 239.0.0.0                    | 255.0.0.0         | 0.0.0.0             | LAN & WLAN |

 

| 4            | 0.0.0.0                        | 0.0.0.0             | 10.37.191.252 | WAN              |

 

*————*——————————*——————–*———————*——————-*

 

And here is the ip-config result for the router in my local computer (Physical Adress censored):

Wireless LAN adapter WLAN:

 

   Connection-specific DNS Suffix  . : 

   Description . . . . . . . . . . . : Realtek RTL8723BE 802.11 bgn Wi-Fi Adapter

   Physical Address. . . . . . . . . : **-**-**-**-**-**

   DHCP Enabled. . . . . . . . . . . : Yes

   Autoconfiguration Enabled . . . . : Yes

   IPv4 Address. . . . . . . . . . . : 192.168.1.23(Preferred) 

   Subnet Mask . . . . . . . . . . . : 255.255.255.0

   Lease Obtained. . . . . . . . . . : Tuesday, April 13, 2021 9:04:01 AM

   Lease Expires . . . . . . . . . . : Friday, May 20, 2157 4:29:41 PM

   Default Gateway . . . . . . . . . : 192.168.1.1

   DHCP Server . . . . . . . . . . . : 192.168.1.1

   DNS Servers . . . . . . . . . . . : 192.168.1.1

   NetBIOS over Tcpip. . . . . . . . : Enabled