At least don't sell into tether. If you want to sell - USD is better than tether. There are exchanges that you can sell in usd. Bitstamp for example. But it's not the only one.
The op said that he is afraid that his money will decrease so he is asking if tether is a good option to secure the value of his btc but he can also exchange it for usd right away .
deciding to save in the form of bitcoin is the right decision
For you yes but for the op , you can see that he is nervous based on his statements so i think saving on btc is not really suitable for him .
if you keep in the form of bitcoin then there will be two possibilities if you experience gains or losses.
Yes but the gains can rarely come than the losses because btc isnt performing good these days .