Welcome to the village. Your language is just fine. Far better than my Italian. As to your question, any scroll that has two arms and hold a blade with tension will swing through somewhat of an arc. So, it will be, at times, either fore or aft and the only time it might be centered is at the exact center of that arc. There has been much discussion regarding this subject but it looks like your saw is just fine. As long as it cuts well and you can control it, all good.