2. For more than three months now, my balance has been standing still because the maintenance and electricity fees are eating up all of my earnings. For how much longer will this go on?!This issue has definitely been the most painful one.
The main reason for that is the steadily growing mining difficulty and you can find the graph displaying it
here, for example.
The Bitcoin network difficulty has been decreasing since 2018 OCTOBER 18, and continues to decline (as can be seen in the graph you referenced)..
The bitcoin network difficulty has been decreasing, yes, but the bitcoin price drops. If there is real mining behind them, still they won't be able to sustain profit for their investors because a bitcoin's value is lower that previous months