Hello and welcome to the forum. Do you weigh the food and are you giving the right amount? AFAIK the usual advice is 1% to 1.2% of ideal body weight. It is so easy to overfeed cold pressed food due to its density.
Is your dog of a satisfactory weight and is he well and healthy? It’s always useful to check teeth and gums and to have them seen by the vet if there is the possibility of a health problem.
We have a thread about feeding the fussy dog here.
I cannot recommend a particular brand but generally dogs are attracted by odour. Because of this, adding wet food as a topper is a good idea. Have you tried adding some fresh food to the Guru eg fish, sardines, chicken, suitable cooked, puréed vegetables - link.
With regards to cost, Zooplus and Bitiba have a selection of cold pressed foods made by Markus Muhle which are good value for money. Some of these are Black Angus, Lukullus, NaturNah and Rotwild. Cost wise, you might have some leeway to add fresh food.