Russian gas: Europe under pressure

On January 1, 2025, Ukraine cut off the taps on the gas pipelines allowing Russian gas to be transported to Europe. kyiv has decided not to renew a five-year agreement with the Russian giant Gazprom and now not a single cubic meter of gas passes through the country. Ukraine thus wants to undermine the Russian war effort, since the shortfall is expected to amount to 6.3 billion euros per year. But this will also cause supply problems for Europeans. The European Union, which had imposed sanctions against Russian oil and coal, had not attacked gas, because it is still too dependent on it. Why has Europe not yet freed itself from Russian gas? Why is this stoppage of deliveries putting the entire continent under pressure? What alternatives are available to him?