I heard that you should change around your routine every couple of weeks but do you have to change everything (exercise,reps,weight,time of week)
or can you just change around 1 thing to avoid muscle adaptation?

Right now the reps of all my exercises are 10,10,8,6 and when i can achieve that i move up 2.5kg on that exercise and try to get 10,10,8,6 again.

If i keep doing this will i avoid adaptation or do i have to change around everything?

How you change and what you change to really depends on the goals.

What are your current goals/program?

typically you change every 6-8 weeks...2 months not 2 weeks. the body doesn't adapt quite that quickly.

change it when you need to change it. When you start stagnating and are not having progress. Upping the weight does not count as variation, its progression.

It can often be a good idea to have alot of varaity in a training regiment, using different exercises each training day, different set/reps. This will keep the body from adapting too fast, however, it will eventually happen.

Jeremy...that's basic linear progression. If you're going to use that method, you might change once you hit 2 weeks of no progress of said movements.

Thanks i understand it better now