Delivery of the western battle tanks to Ukraine. What is at stake and how it can change course of battles in 2023

Despite the German approval to send the "Leopard 2" tanks to Kiev, after a clear hesitation, and amid the Ukrainian dependence on the role of these tanks in the path of the battles, its way to Ukraine does not seem easily.
European countries are facing several problems in providing Leopard tanks that they have pledged to present to Kiev, according to the New York Times.
These tanks are not available in adequate numbers, and they face logistical and technology problems in preparation for the entry of battles. As well as training Ukrainian soldiers to use it.
Why were these factors not among the accounts of European officials when they pledged to hand over Lubard tanks to Ukraine? Who takes responsibility for delay in providing it? And to what extent was Kiev on these tanks? 

 DIF Executive Director Petro Burkovskyi explained to Sky News Arabia how modern battle tanks can change the course of war and debunked Russian disinformation about battle of Bakhmut:

• Russian news about "capture of Leopard with Polish crew" cannot be trusted
• Ukraine uses no less than 1000 modern Russian battle tanks abandoned by Russian troops since beginning of war
• Ukraine will get up to 300 tanks with hundreds of infantry fighting vehicles, air defence systems and relevant training of crews by summer 2023 and it is exact number which is required by Commander-in-Chief Valerii Zaluzhnyy to conduct offensive operations
• Between January and February 2023, according to the General Staff of Ukrainian Army, Russian army lost 40,000 troops, which is same number of casualties Russians suffered between February and August 2022. If Russians stick to such tactics, they will be exhausted by summer and give Ukrainian army a good chance for counter-offensive.