It's all about the bond you have with your dog. He must be focused on you and look to you for the next command
It is but it is also about the phase the dog is going through.
In my opinion the teenage phase is not the time to be teaching new skills or altering commands.
Get a long line to keep him safe ( in my experience dogs don't always transfer behaviour they exibit when using the line anyway ) and let him off when you can so he can still have a good run.
Sometimes I think the teenage phase is something us dog owners have to "get through" and then commence traning afterwards.
He's still only 5 months, and I agree, I wouldn't be training mine yet. 6 months minimum for anything other than basic such as sit, stay and recall to his name. Persevere with the basics and it will come good
6 months is a little early imho to expect training to sink in with a cocker!
i think from very recent experience mich and i have a shared view that between 5 months to 1 year it is a difficult time to get any effective, reliable and consistent results from training. this time frame varies of course from dog to dog. when my dog hit 11 months his 'hearing' came back and it is far far easier to train him with good results. Training sessions in the adolescent peak are frustrating and no matter how 'attractive' you make yourself you sometimes lose out to another dog, a bird or a pile of horse poo.
The gamekeeper that bred jarv doesn't begin training his spaniels until a year old for beating or picking up, and i can see why.
perservere with dyllan, be consistent - some days will be good, some bad
most important thing is to have methods that will keep him 'safe' which will range from a long line to smelling like a german sausage factory with pockets packed full of sossij & livercake