Germany beats France and switches to Russia.

In late September 1914, the French Government has capitulated and the British evacuate.

Germany and Austria Hungary (no Ottomans in this scenario) then start an offensive into Russia. IOTL, Germany sent roughly 50% of their troops to the Eastern Front in the Spring of 1915 and soon started the Gorlice-Tarnow Offensive/Great Retreat which ended by October. The Germans and Austrians combined had a slight numerical superiority during this period. The Germans alone lost 447,000 men during the Great Retreat and the Austrians probably lost more.

What if the Offensive in Galicia and Poland started in the Autumn of 1914? Russia would have no ammunition shortage that they had in 1915 and 1,000,000+ Russians would still have not been casualties.

How long does it take Germany to take Petrograd and push past Belarus and Ukraine? And how many casualties would there be on the Central Powers side?
In late September 1914, the French Government has capitulated and the British evacuate
This is under the assumption that Russia never attacks the the central powers when The Germans are still in Belgium and so resources wouldn't be spent on the east causing the Schlieffen-moltke plan to fail

So how does this happen?
Stolpyin never takes power in the russian empire and so the economic and industrial reforms never take place and Russia's railroads are shit so mobilisation takes longer

And about that last question
They would take petrograd Probably around 1916(because of Russia's shitty railroad problems) but the russians would either be in a civil war at that time or would probably surrender and Germany wins