Helga, welcome to you and Al. You have gotten good advice. I just wanted to chime in that both my diabetics were started in that insulin (vetsulin here in the states). Beau was raised to 7u once a day, while he was still eating dry food and it was way too much. I was also not testing at home then, but taking him to the vet weekly for tests, and then for a curve, where he hypoed for them (probably was dropping very, very low at home too and I didn't know it).
What I wish I had done was learn to home test right away instead of waiting six months. That and get rid of the dry food. When I did that, with help from folks here, his dose ended up being just under 1u twice a day. And I found that most cats on that insulin were around .75u to 1.5u twice a day. Not 7u. That dose really scares me.
I love my vet, she is very good too, but she didn't know that much about feline diabetes. I really believe that this disease must be managed at home, not at the vet. She also wanted to wait until he stabilized to address things like diet. I don't think he would have ever gotten "stabilized" if I didn't test and change his diet.
I switched Beau to another insulin, after 2 years, that I bought from Canada over the internet without a script. It is called levemir. It is a much better insulin for cats than caninsulin. Beau is in remission now, diet controlled, and I adopted a second diabetic cat, Jeddie, so he wouldn't be put to sleep. He is on levemir now. He also was a handful when I got him, and bit me hard when I tried to test him, but it wasn't long before I could do that fairly easily (I wrapped him in a fleece blanket so only his head was showing). How, a year later, he purrs while I test him. I test, give the shot and then give a treat - usually boiled chicken breast. Treats really help get them to accept the process as something good.
Hang in there and ask questions. Maybe someone from here lives nearby you and can come over and show you how to test?