What if instead of the first active one from the next package, I took a placebo from the previous one?

You did not write what pills you are talking about. Please provide the trade name of the drug - this will make it easier to find the answer you are interested in in the context of a particular drug. If you mean contraceptive pills, most likely two-component pills, then taking a placebo instead of an active placebo pill is tantamount to skipping a pill. Placebo has no hormones, so it's as if you forgot to start a new cycle. This means losing protection against pregnancy and the need to protect yourself mechanically for at least 7 days. It can also be problematic if you have had sex in recent days. In the leaflet of your preparation, please look for information in the section "Skipping one tablet in week 1". In general, the recommendations are as follows or similar: "Take the missed tablet as soon as possible, even if it means that you need to take two tablets at once. Subsequent tablets should be taken again at the usual time and additional safeguards, such as condoms, should be used for the next 7 days. If you had intercourse in the week before you miss a tablet, you may become pregnant. In this case, contact your doctor." I enclose additional information: https://www.gdziepolek.pl/artykuly/jak-prawidlowo-stosowac-antykoncepcje