The order you found is the full text of Hitler's last Fuhrer Order dated April 15, 1945, under the rather delusional assumption that the Red Army would be crushed trying to capture Berlin in what German propaganda referred to as Endsieg, or Ultimate Victory.

The greater context of this directive was that it was sent out the day before the first Soviet artillery volleys on Berlin on April 16, signaling the beginning of the Red Army's advance to capture the German capital. The Wehrmacht had a total of 36 (woefully understrength and undersupplied) divisions of around 750,000 men to defend the city against over 2 million Soviet soldiers called up for the battle. What was hoped to be achieved was no less than the complete destruction of the Red Army's forces either outside or within Berlin. How they hoped to achieve this was through a flanking maneuver from the north led by Felix Steiner's III SS Panzer Corps to encircle and destroy the Red Army as they approached the capital....somehow.

As for the chances of success, it was negligible, if not impossible given the Panzer Corps' situation on the ground. While Steiner's III SS Panzer Corps looks like a mighty force on paper, in reality it only consisted of 3 undersupplied battalions, and only a few working tanks. When Hitler gave the order for Steiner to attack, the Soviets already had his force north of Berlin pinned down and on the defense. /u/davescout44 does a good description of what Steiner's forces were facing in this answer.

To paint a clearer picture of just how impossible it would be for Germany to achieve victory at Berlin, lets look at some numbers.

For Operation Barbarossa, Germany and its Axis allies had 3.8 million men, ~3,500 tanks, over 3,000 aircraft, and over 25,000 artillery and mortar pieces amassed to invade the entirety of the Soviet Union.

For just the Battle of Berlin, the Soviet Union dedicated 2.3 million soldiers, over 6,000 tanks and self-propelled guns, 7,000 planes, and over 40,000 artillery pieces. A force very much comparable to the invasion of the entire Soviet Union was amassed just to take the German capital.

By April of 1945, Hitler's hopes of 'Ultimate Victory' were outright delusional, with an overwhelming amount of accounts that Hitler's grasp of reality was fleeting at best by the end of the war by his peers.

Many thanks to u/quiaudetvincet for linking my response from a few months ago. There are just a few things I'd like to add to your great answer.

Hitler had claimed multiple times that the Red Army would be destroyed at the gates of Berlin or within the city itself. This claim on its own does have some basis in reality. He could call upon recent history with the spectacular Soviet defense of Moscow in the winter of 1941/42. Here, the Wehrmacht had pushed to within a few miles of the Kremlin before being driven back by a Soviet counterattack using fresh troop reserves. One of the big differences between the defense of Moscow in 1941 and Berlin in 1945 is that the Germans simply did not have the reserves to call up. Stiener's force would have looked respectable on a map, but did not have the slightest chance of stopping the Soviet juggernaut closing on Berlin.

In a Führer Order dated April 14, 1945, Hitler made allusions to the routing of the Turks outside of Vienna in 1683. "The Bolshevik will this time experience the ancient fate of the Asiatics." He believed that the Soviets would be stopped at Berlin because they HAD to be stopped at Berlin. Despite many of Hitler's generals giving very accurate reports on the numbers of Soviet forces arrayed against the capital, Hitler choose not to believe them. This piece of information is important, because it call attention to the fact that few member of the German high command shared Hitler's beliefs. In a fitting expression of irony, Vienna fell to the Red Army on April 14. That is why the Führer Order for April 15 includes the line, "Berlin remains German, Vienna will be German again, and Europe will never be Russian."

On April 20, Hitler's 56th birthday, Soviet artillery began shelling the center of Berlin. Hitler took this as a personal affront (as the Soviets had intended it to be) and was incensed to learn that the artillery was of medium caliber and not heavy guns, which meant that the Soviet gun batteries were closer than expected (This event is [recreated] (https://www.youtube.com/watch?v=Xt3v7tigsro) in the movie Downfall). The Soviet plan was to encircle Berlin from the north and south, and Steiner's III SS Panzer Corps appeared to be in an ideal location to attack the flank of the northern Soviet pincer. But neither Stiener's attack, nor any other, had a chance of saving Nazi Germany at this point. When Hitler received word that Steiner could not break through to Berlin, it is understandable to see how the bottom had fallen out on Hitler's house of cards. This would be the German people's own "Götterdämmerung" (the name of an opear by Richard Wagner, which translates to "twilight of the gods".) If the Soviets could not be stopped, Hitler believed, then Germany had no reason to survive either.