is it a good idea to take 20g per day for 5-7 days and then after go back to 3-5g per day?

The traditional method of creatine loading—taking 20 grams per day for 5-7 days followed by a maintenance dose of 3-5 grams per day—is an approach that was popular in the past. However, it's not necessary to load creatine in this way. A consistent daily dose of 3-5 grams of creatine monohydrate is generally sufficient for most people to achieve and maintain the benefits of creatine supplementation. This method is not only effective but also more economical, as there's no significant advantage to loading in terms of increasing muscle creatine stores over the longer term 1.