Windows – Client wont boot via PXE and WDS [Resolved]

So the past couple of weeks I've been trying to get our WDS running again.
The person who set the WDS up doesn't work here anymore and very little is documented about it.
I managed to get the majority of the problems out of the way that I had on the server itself, now I'm trying to boot a client over PXE but I keep running into errors with several DHCP Setups I came across on Google and Technet.

We use cloud managed Meraki switches and have a VLAN set up on the switch the client is hooked up on (specifialy for PXE Boots).
The WDS and DHCP Server are in the same subnet/VLAN but in a different one than the client. The WDS is a Windows 2012R2 and the client is a DELL Optiplex 790.

The way the VLAN for the client was setup originaly it ran a DHCP with the Nameservers specified and DHCP Options enabled (boot server, boot file and option 60 set to PXEClient (String)).
Using this setup the client got an IP from the DHCP but then returned the PXE-E55 error that he did not get a reply from the proxy DHCP on port 4011.
I tried several other things like removing option 60 but there it doesn't even give me an error code, it just shows the IP, Mask, DHCP and Gateway, says "TFTP." and then just exits the boot agent.
I even updated the BIOS just to be sure that it wasn't an issue.

By now my basic knowledge is used up and none of the solutions I found on the web helped.

Does anyone have any tips or expirience with similar problems who could get me on the right track to narrow down the problem?

Thank you all in advance!

EDIT: Okay since I'm new to this network and the job, I just found out that the DHCP is on the switch and per VLAN we have a DHCP each. Meaning that the WDS has it's own DHCP it's comunicating with, as well as the PXE Client has it's own DHCP to comunicate with. But WDS and DHCP are not on the same server.