Your written English is fine. Welcome. You will find sound advice here from knowledgeable people; people who work hard and exceed their goals, only to make new ones.
84kg and 168 aren't terrible stats. Even if you are 20% body fat.
Now for the bad part. More muscle will come from good healthy eating and training with resistance for a long time. Most likely you don't eat enough protine and you eat too much sugar or fat.
Body fat reduction comes from eating less energy than you use in a day.
So the two things can be done at the same time but both results will take time to see.
If you follow certain members like cj and send0 they are always helping new people with reduction of body fat and how to put on muscle. No need to chat with them. They are both too busy to take your hand. But they have posted a lot on the subjects in the past. Just follow them and read the advice they have given others. That is how the forum works. Most questions have been answered somewhere here.
If you want help from many people personally, start a training log. Post what you eat in a day. Post how you train. Post a picture or two. Then tell them what you want. If you aren't certain what to do read other people's logs.