Needing help asap

Make renault 19 bebop, mile`s 87000, year 94, size 1.4

what it is I have noticed that I have lost power so I looked under the bonnet and there was like a burst exhaust sound coming from my manifold so I took the heat sheild of and noticed it was not the manifold but the part which goes into the exhaust but I dont know what that part is called I tryed putting some gungum round but that did not work need help please thank

aother thing my horn doesn`t work any ideas

cheers mike