Hey there
In june & July I bought Digibyte & Stratis & Siacoin with all my bitcoins, till now I lost almost 80%
What can I do, HOLD or Sell or What!
You haven't lost until you sold

Well OP's opportunity cost should now be in the hundred thousands or million $.
Selling out altcoins for the sake of bitcoin does make sense to me, selling out bitcoin for ethereum, monero, litecoin and other famous altcoins does also make a little sense to me but giving up on all of the bitcoins for buying Stratis and other such altcoins, sorry to say, but makes zero sense.
I think this would have become his greatest regret of life. Bitcoin is now touching 6k dollars. The best is to buy bitcoin again.