Thanks N0One!

I am also on Binance.

So... you do the same way as I do..  Except I was from begining trading in ETH (never in BTC because of the fees).

It is complicating to watch in both currencies (USD, ETH) .. I mean always to recalculate the real value. Lets say, a little bit annoying.

And yes, one feels uncomfortable to let trades sit for a longer time. When an Alcoin comes down, I at first need to buy ETH from USTD (Theter) and then buy the Altcoin. But This costs time - and in the meanwhile the altcoin increased again..
Sometimes there are hudge spikes down, but you cannnot cach them when you need too long until you are ready to buy.. Especcialy it happens at night while you are sleeping or on day when you are at work..
So I see, setting a low buy limit is not really possible (senceful). What a shame!

Was hoping someone found an "other" solution..