Post [Q] Lagging after sending sms

After using my previous mobile - HTC Desire, I've decided to backup all my sms and contacts and then to restore it on S5 using Super Backup app. So it worked nice, all contacts and sms were restored. On my HTC Desire there was one problem with sms - when the number of sms gets around 1000-2000 in one chat or smth like that, the mobile starts to lag receiving/sending sms.
I thought this won't arise in S5. Yes, it works much faster, but in one chat (around 7000 sms) it's lagging for 3-4 seconds, when I receive or send SMS. In other chats it works fine.
So the question is - how to get rid of it? I don't believe that S5 with such good characteristics is lagging with sms.

P.S. Sorry for my english.