i'd get back in slowly, start saving up coupons etc. Get one of the meta ninjas and try out some lineups. If you still lack interest then it's better to just log in and claim the rewards. See how it goes because 80k power isn't that low and you should be fine slowly progressing your way back up

But 40k its huge difference, i can play but its a real suffering for me.

Most of the events are cross server, you're never really competing with anyone in your own server except for 3 things, GNW, Ranked battle & Nine Tails- and it comes down to whether you're bothered by not being in the top 3.

It depends if we're talking about 40k between you & the top 3 or 40k between you & the average player, if it's 40k between you & the average player, I'd think about restarting personally because I'm a little competitive & I'd assume you wouldn't be here asking if you weren't also.
I'd also base my choice on what you have, will you lose a lot of good ninja by restarting?

If it's 40k between you and the top 3 then it's fine, as p2w'ers will always be paying to win on a new server or an old- the top person on my server is 40k ahead of the person below him & 50k ahead of me, just to give you perspective.

80k BP is big for f2p and you didn't get there without time and patience. Imo stay in your server if you only want to enjoy playing the game and watching your character grow. But catching up with top players is going to be impossible if you aren't going to spend. If you want to be competitive you have to start over.

will if you beat them at 1st position kick ther a$$

I took a break for about a year and came back and at the time I had 65k power. Month and a half later I now have almost 88k power. Only have 2 outfits (Samuri and cat one you get from grocery store) and I haven't spent coupons on events yet. Still saving for Jonin Minato. I wouldn't expect you to be competitive for a few months, but it will start to slow down and you will be able to catch up in power. Gonna take some time though.