Just a quick FYI: this is an english forum. While you can use a different language, you should also give the translation (google translate generally is enough). Also says so in the
rules.
Now to your question:
The version available here does not allow you to change your penis size at character creation and so far there is no event changing it in the game.
It is possible to change it using the browser console, but a little tricky because the dev added a check and reset when you visit the bathroom. So you first have to remove that check, afterwards you can edit the variable whenever you want.
To do that you have to grab the offline version, open the html in a text editor (I prefer using notepad++), search for "State.__getUpperName__.player.body.sex.size=2" (without the ""), ignore the first time you find it (that is the character creation part), the 2nd hit is the reset, delete it.
Now open the html in your browser, after character creation you can now use the browser console (F12) to change your penissize by entering:
SugarCube.State.__getUpperName__.player.body.sex.size=1 (for smallest, 2 med, 3 big dont think the others are implemented yet).