Cant get logging element

The following is one way to select those fields and login into that website (fields are in an iframe):

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

chrome_options = Options()
chrome_options.add_argument("--no-sandbox")
chrome_options.add_argument("window-size=1280,720")
webdriver_service = Service("chromedriver/chromedriver") ## path to where you saved chromedriver binary
browser = webdriver.Chrome(service=webdriver_service, options=chrome_options)

wait = WebDriverWait(browser, 10)

url = 'https://portal.librus.pl/rodzina/synergia/loguj'
browser.get(url)

wait.until(EC.element_to_be_clickable((By.XPATH, '//a[@class = "btn btn-third btn-synergia-top btn-navbar dropdown-toggle"]'))).click()
print('clicked to open dropdown') 
wait.until(EC.element_to_be_clickable((By.XPATH, '//a[@href="/rodzina/synergia/loguj"]'))).click()
print('clicked to get the login interface') 
wait.until(EC.frame_to_be_available_and_switch_to_it((By.XPATH, "//iframe[@id='caLoginIframe']")))
print('switched to iframe')
wait.until(EC.element_to_be_clickable((By.XPATH, '//input[@id="Login"]'))).send_keys('My username')
print('located and wrote into id field')
wait.until(EC.element_to_be_clickable((By.XPATH, '//input[@id="Pass"]'))).send_keys('My password')
print('located and wrote into password field')
wait.until(EC.element_to_be_clickable((By.XPATH, '//button[@id="LoginBtn"]'))).click()
print('logging in now...')

This will also print in terminal:

clicked to open dropdown
clicked to get the login interface
switched to iframe
located and wrote into id field
located and wrote into password field

Selenium setup is linux/chrome, you can adapt the code to your own setup, just observe the imports and code after defining the browser.

For Selenium documentation, please see https://www.selenium.dev/documentation/