Secondary cipher challenge part 6

Here is the final part of a six-part challenge. Can you crack the final message?
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

This is the last part of the Secondary Cipher Challenge.

 

Part 6

Kn pqf gcv iglh vpzu, gitg ngwp fweg! Elka fpp aca mgcc vwlis! Xjqj opwuixg heu meeccrbvf hmvp r Xtkgvvtp gkxygc yuqei elg svahstl tkcgnm. Pqf wjwlno jkvu qfx cjfwe xjm Bcdmusz opxjwu qy xjm zpeitvvv, hlkky gitnizpd e omkjzh qn ugnvaxkkyk vpzu ecrm fh nmrpvt. Tx kvmqwzga wkyhkvx vsi pcddpv qn cgexgzj dpxymvp cirmrvph dtfevw qn cgexgzj ky xjm tkalgzkgix. Vpzu tw nqbgwc vw sg l qwtkkapg ww vsi nmeiel qn kjp oggnqch. Kn kjpvg iig prqcxj cirmkkemqvj, azy oqxje xjme dp edtv vz hgbvtxmpm kjp pgvxvs sh byg viaefto fa krnnynikkyk vpv hlgvwiu zj vpvup pgvxvsw cvu nzsmqei qst kfoxsp nreesta. Njj rqb ktj epl ttpevm pqfv qee ettjmi cyh vmjv tx qv pqfv hzzgyhu vfy!

 

If you want to work on a computer to solve the problem, you can download this cipher as a text file which doesn't contain any line breaks.

You can use the Cipher Challenge Toolkit to help you decipher it.  

 

If you have managed to solve Part 6, do submit a solution to tell us the techniques you used to solve the Cipher Challenges.