Many (not "most) convoys made it through intact becaise the Atlantic is a large place.
Perhaps a few convoys were detected by "chance", but the German Navy and Air force were conducting specific search patterns. This is not called "chance", but "deliberate".
This statement: "And, I see that you are falling in the code breaking trap" appears to come from deep within the conspiracy zone - yes the German Enigma code was broken.
And this is a fascinating comment:
"what arrived in Britain was mainly determined by the amount of goods that was going to Britain".
This part, however, appears to be the remark of a person who desires that history changes to their liking and/or refuses to accept the historical truth:
"the U Boats had no influence at all"
Most convoys were detected, not by U Boats, but by the German B Dienst ( The German Ultra ),which was breaking the code of the RN/USN.
But,the B Dienst could not give a detailed information about the direction of a convoy and of the place where a convoy would be , that's why the B Dienst messages were mostly useless . And, if/when they were precise, than was there still the problem to concentrate a number of aircraft to attack the convoy , and when there were enough U Boats available, there was the problem that they needed to have sufficient fuel and ammunition and if they had sufficient fuel/ammunition, there was the problem of speed :U Boats were slower than fast convoys .The Torch convoys had no losses,because the B Dienst could not tell where they could be found, because there were not enough U Boats with sufficient fuel,ammunition and speed to attack them , NOT because of the information from Ultra .
The result was that in most cases Dönitz could do nothing with the information he received from the B Dienst .
This also means that it was the same for the Ultra messages : Ultra was REACTING on the messages of the B Dienst ,and ,as these messages had only a low threat level, Ultra could do not much .
How many convoys were redirected because of an Ultra warning ? Only a minority .
And how many convoys that were not redirected ,were attacked ? Only a minority .
And, what were the losses of the non redirected convoys that were attacked ? Very low .
A convoy that was not redirected was not doomed and a convoy that was redirected was not saved .
And it is obvious that the amount of goods that left the US for Britain had a very big influence on the amount of goods that reached Britain : if during a month 1 million tons left the US for Britain, not more than 1 million tons could reach Britain even if there were no attacks from the U Boats .
It was the same for NA : in November 1941 the Italians sent 79000 ton of materiel to NA of which 30 000 ton arrived (37 % ) ,in December 1942 they sent 13000 ton of which 6000 arrived ( 47 % ) ,what was better :47 % or 37 % ? It is obvious that 37 % was better ,and if in December 1942,100 % arrived (13000 ) , it is obvious that 37 % was better ,because more was sent in November 1941 .
The U Boats had no possibility at all to starve Britain ,and the mistakes from Dönitz make things even worse for Germany . Mistakes as Drumbeat ....
The U Boats failed in WW 1 ,they were doomed to fail in WW 2 .