AVG tick at 3-6 ticks

I know, that this topic often has been questioned, but I found nothing for especially my case. I am running a Minecraft forge server on the version forge-1.7.10-10.13.4.1558-1.7.10-universal with these mods (for the version):

backpack1.7, Custom-Mob Spawner, Custom Npc's, Dragon Mounts, MoCreatures, fastcraft, Lots of food, millenaire, vending block, worldedit

My server has 4 GB Memory to use and he does use round about 200 mb and there is 97 % free memory, maybe thats the problem, but the avg tickrate is everytime about 3 to 6 ticks per second and obviously it is lagging especially with the npc's. My usage of ram and CPU with minecraft and the server running is at 20% CPU and 8,75 GB RAM of 16 GB. If you wanna see my .bat here it is. I have no idea what causes the lag, but on a forge server without mods and with a fresh new world, just generated few seconds before I connect the lag is the same. Is there a problem with my internet connection or is the server using to less ram? LG Lenin