If I'm understanding right, you're stuck on a mission that requires you to reach Silver 1?

I know the arena missions can be challenging, but they're certainly do-able, just might take some grinding to level up your champs and some refreshes. 

We've all had to go through it, so it's certainly possible to succeed. I know the arena ones can be time consuming, it took me like a month to get a great hall bonus to 10 (before the put the bots in arena), so I know the time it takes can be frustrating, but it's certainly possible to do given enough time.

What does your current arena team look like?

the arena was definately alot harder 6 or so months ago, BOT teams were added to help progression as alot of the player base was stuck with that mission alone let alone reaching higher gold tiers

build your team with the aim of the team complementing each other eg speed lead aura for arena champ, decrease defence debuffer, then say increase attack or stun or sleep then in comes a AOE nuker say Kael  

as your arena team gets stronger you will find your progression through the lower arena tiers will jump and become easier 

speed is king in arena however in saying that if you have the champs to survive the opponents going first and go 2nd you can still get the win that way - i had no speed lead for so long in the arena that i build my arena team around defence and surviving the first attacks then my team would go and rip the opponents team apart.

good luck and trust me we all were feeling you are right now at some point, it only takes that 1 champ to turn things around 

post your champs via screenshot in this post we can have a look and see if we can find a team you can try out 

also team power not necessarily means the teams strong - if they have high resistance that will also push up the team power of the team 

i regularly find teams 100 000 k more team power than mine and wipe them easy its more about how each champ fits the arena team and the overall team synergy if you get what i mean as such