Of course everything what you forget can be bought here. Norway is an expensive country however and higher costs do not guarantee a higher quality.
Here is my list with important things (learned myself by experience). Priority number one is your photo camera.
01. Backpack (for walking, hiking, biking)
02. Boots (even the forest can be too wet on some days)
03. Rain coat and cap.
04. Warm jumper of sweater, warm socks, next to cotton.
05. Something warm to wear in the night.
06. Special shoes and socks for walking/hiking/nordic walking, and poles
07. Shirts and short trousers for when it is really hot.
08. Get informed about ticks
09. Don't forget your medicine.
10. Where is water there are mosquitoes.
11. Take at least one set of thermal underwear with you.
12. For Spring and Autumn you need more warm clothes and hardly something cool.
In winter are needed: woolen or good quality fleece clothes; special coats; caps; gloves; more heavy quality thermal underwear; double layered trousers; socks; good quality hiking shoes; sun glasses to wear during driving the car because of the blinding white of the snow, and the shining melting ice on the roads.