I think its a little bit complicated to add an item and edit that new entry afterwards to select my bid amount. Maybe you think about adding a second field with the (optional) bid amount.

And I think its strange that the app asks me if it should activate the bid after I added one. I mean.. why should I add a bid without using it for sniping?!

Many users add items in bulk, then they check what they want to snipe from that list.
Some just add for watching purposes, while others may add it as a backup in case if other snipes failed.
These are the most popular conditions, but there are many other situations where items is being added without setting up a snipe.

For Windows client there is a way to add snipe amounts quickly:
If you navigate to the "My Bid" cell and press "F2", you can edit your snipe in-place. Once you hit "Enter", it will be saved on the remote server.

This is how I would prefer it:

2017-04-15 21_53_42-Myibidder (Online) - maxrev_de.png

I understand and consider it for future releases.
Thank you for clarifications.