Short answers, pulled from the story.
Starting in 1549, the Ottoman Empire supported smaller Turkic and Islamic vassal states within modern Russia. This support brought the two empires into direct conflict over centuries of territory.
The Treaty of Küçük Kaynarca signed on the 2nd of May 1774 granted Russia passage to the Black Sea. It also allowed the Russians the privilege to intervene in the Ottoman Empire on behalf of Eastern Orthodox Christian populations.
The Russian Soviet Federative Socialist Republic was the first state that formally recognized the Kemist government of Turkey in March 1921. The Treaty of Moscow signed on the 16th of March 1921 between Lenin's government and the Grand National Assembly of Turkey followed bilateral treaties concluded earlier that year.
On the 19th of March 1945, Soviet Foreign Minister Vyacheslav Molotov advised Turkey's ambassador that the Soviets were unilaterally withdrawing from the 1925 Non-Aggression Pact due to deep changes occurring during World War II. The decision included a claim by the Soviet Union to parts of eastern Turkey including Kars, Artvin and Ardahan.
On the 24th of November 2015, Turkish F-16 combat aircraft shot down a Russian Sukhoi Su-24 during an airspace dispute close to the Turkish-Syrian border. Russia imposed economic sanctions on Turkey including limits on business operations and restrictions on imports of Turkish products.
Turkey has broken ranks with all other NATO member states by continuously refusing to impose sanctions on Russia for its aggression and occupation of Ukraine. On the 28th of February 2022 President Erdoğan confirmed that the straits would be closed to prevent an escalation of the war while also pledging to maintain relations with both Ukraine and Russia.