Hello Edgar. I’ll be glad to clarify how the Time as highest bidder system works.

You gain levels by staying as the highest bidder for an auction. This means you have to hold the lead position of an auction for at least a full second before the green bar at the bottom your screen (also known as the time as highest bidder meter) will start filling up.

When the green bar reaches the end of its corner on right, you will gain a level. When you gain a level you will be rewarded with bids which you can claim by pressing the button next to the green bar. The number of bids you receive will increase as your levels increase, but so will the required amount of seconds as well. There's not a limit in the number of levels, so that you can always get free bids, no matter how much you play!