First trip to Europe

depends on where you are. If you could get a proper package tour flying into London, out of Hamburg with connecting flight in the middle it may be worth doing. If you had to book the flights as single legs any discount on bundled hotel prices could be lost.

Airlines from London to Hamburg are:

BA and Eurowings (low service arm of Lufthansa) from Heathrow

Easyjet from Luton or Gatwick

Ryanair from Stansted to Lubeck (they call it Hamburg but their policy of airport naming is legendary) Lubeck is a very nice place but it's quite a long way from Hamburg.

Easyjet and Ryanair may offer really (stupid) low fares 3-9 months in advance (don't forget the additional luggage fee) but if left until a few weeks beofre departure could be more expensive than BA.

Arrive in London. Either stay a few days or longer for a visit, or leave on a connecting flight. There are connecting flights to Hamburg. Or, if you want to consider the land route: take the train, using the northern route through Belgium and to northern Germany or the central route via Paris and Frankfurt, then to Hamburg on the iCE.

try Easy Jet; https://www.easyjet.com/en

They can sell combine air hotel or hostel from London to Hamburg

Which hostel are you staying at? The private independent one "Generator" is located opposite of the main train station , Hamburg Hbf. Take the Kirchenallee exit , turn right, all the way to the end of the station, it's across the street at the corner, multi story building. The HI hostel is located at Landungsbrücken, one stop on the S-Bahn (subway) from Hamburg Hbf., across the bridge ona hill close to huge Bismarck statue.

Best way to find flights is www.skyscanner.net and select monthly view.