Hi Manuel, welcome to the forum
That’s one deep river you are fishing, a couple of questions to start with, do the bream feed on the bottom or can they be caught off the bottom for example can you catch them before the bait settles , what size fish are you catching?

Questo è un fiume profondo si pesca, un paio di domande per cominciare, fare il feed orata sul fondo o possono essere presi dal fondo per esempio, si può prenderli prima che l’esca si deposita, che formato pesce stai recuperando?

Manuel
Well with never seeing the river this is how I would tackle it
An open ended feeder with no holes in the feeder

i would use a feeder like this to stop the bait coming out before the feeder hits the bottom
Ground bait mix, well I would have a mix containing brown crumb and either sensas lake or river , mixed on the damp sticky side,
Bait, chopped worm, casters, dead maggots , (and probably sweet corn, depending on how the fish are feeding )
Hook bait, all of the above, and a cocktail of , maggot caster, maggot worm, caster worm , even double worm?
Hook size, depending on how the fish are feeding , size16 to size12, a larger hook if the fish are feeding well
Hook length size and length, 0.12 to 0.18 , hook length from feeder to hook anything from 45 cm to 1 mt , depending if the fish are on the bottom or feeding off the bottom
Rig, if slow moving which I assume it is, I would fish with the standard paternoster
Main / reel line, in the UK iwould use a 4 to 6 lb breaking strain line, so in metric it would be 0.18/0.20
I would start by casting out no hook length on the rig, with the feeder full of bait say 10 times just to get some bait into the swim, then tie the hooklength on, and casting say every 5 minutes until the fish start to feed
Like I have said, without seeing or fishing the river it’s hard to say exactly what to do
If you do not understand any of the above please get back to me