One thing you must not do i loose confidence Slick ponds are very often in the first year or two a steep learning curve , we can only anser yur questions in general and suggest answers, sometimes it can all seem a trifle confusing.
Your best bet is your local club who have boots on the ground so to speak and can come out to help you face to face, to acctaully stand by the pond test your water perameters, to look at your problems and make suggestions.
Remember what I first told you its all about the fish not the size of them or the size of your pond its the love of koi that binds us all together into a group.
Between them your local section has yeaars of experiance, so what if they have bigger more expensive koi o larger ponds comapred to some members in our own section our pond is a puddle , due to circumstanes I cant affoard the really exppensve fish nor can we build a bigger pond but I learn and pass that knowlege on
I'm the nearest person to understanding your weather variatons etc sadly though I dont live next door if I did I'd be out helping you
Dont fall into the trap of well I dont know this or that , one thing all of us will tell you is you "NEVER" stop learning in our hobby , there are always new ways oof doing thngs
Buy a number of books and educate yourself some on the workings of pond and koi health "YOU'LL BE GLAD YOU DID".
When we first started I lost goldfish after goldfish then on my birthday 28 years ago Val bought me the now Interpet Manuel of Fish Health back then it was Salamander and now 28 years on we are still going strong even having to relearn much of what we knew but this time in a pond situation .
In that I was lucky to have the Head of the BKKS Health standards Committee in our section who was willing to be my mentor .
Its not somehing we learn overnight , I always tell a novice "dont run before you can walk", the ones who listen last the course those who dont last a few years and quit........
Go into my link here and look into buying the books that I think suit the UK koi keeper and written with UK and European koi keepers in mind , the Interpet Manual of koi Health would be another good book for you to educate yourself from both have been extenscively rewritten and are up to date.....
https://www.gardenpondforum.com/articles/our-updated-library-with-reviews.11/
Otherwise you may only serve to confuse yourself Slick, by the way the first ever book I still use from time to time its dog eared and falling to pieces but it turned us around and I'm glad it did as I wouldnt be around , I'd infact be dead the PTSD I suffered from would have destroyed me.
Ask a friend of mine Big Lou who is a fellow sufferer how dark a place it takes you too
Exagerate that by my alcohol intake from my military days and you'll see where it was leading me too "an early Grave" even my mother thought I'd not get passd my 30's....
Yet here we are 58 on March 4th with a lovely lady who stuck by me the whole time, founding fathers to a section and in the koi magazines koi hall of fame 2009 happy that we'll hopefully keep this hobby going till our late 70's
Back on track though for a few quid the cost of the books and help from your section as well as GPF and you'll be passing on that knowlege to others 12 months on .
Dave