Are bad things in life Satan's doing or God testing/punishing me?

From an atheist Christian perspective, the answer is obviously no. The bad things that happen in our lives are either blameless accidents or the consequence of bad actions by ourselves or others (without any intermediary directing things around so there is a bad outcome). And since all people are fundamentally good, bad actions by ourselves or others are themselves a consequence merely of a failure to properly educate the responsible party as to right or wrong, so that moral knowledge is internalized (rather than the simple academic awareness that other people think it's wrong)--which means that we must share the Christ's brotherly love and compassion with them so as to help them see the error of their ways.

satan was formerly an angel created by god.This angel was very pride of his wisdom, power and beauty and therefore began to disobey god in everything.As a result of this god cast him down to hell but he (The fallen Angel or The Lucifier)started to challenge with god in order to spoil the mankind that god so lovingly created for himself and to gather a group of evil people for his mission against god.So, if a person couldn't endure a temptation from Satan and begins to do evil, then the judgement and punishment of god will come upon him.Therefore we the human being have to be submissive to the word of god to the point of death just as the Lord Jesus Christ who endures all temptations with much patient to the point of death.

James 1:2-3 is very clear on this - trials (bad things) are used by God to perfect you.

Consider it pure joy, my brothers and sisters, whenever you face trials of many kinds, because you know that the testing of your faith produces perseverance. Let perseverance finish its work so that you may be mature and complete, not lacking anything.

Temptation, often a related concept, however, is not from God, per verses 13-15:

When tempted, no one should say, “God is tempting me.” For God cannot be tempted by evil, nor does he tempt anyone; but each person is tempted when they are dragged away by their own evil desire and enticed. Then, after desire has conceived, it gives birth to sin; and sin, when it is full-grown, gives birth to death

As Hebrews 12 reiterates this, saying:

have you completely forgotten this word of encouragement that addresses you as a father addresses his son? It says, “My son, do not make light of the Lord’s discipline, and do not lose heart when he rebukes you, because the Lord disciplines the one he loves, and he chastens everyone he accepts as his son.”

Finally, from 1 Corinthians 10:13 it is clear that when these bad things occur, God promises to give you strength to overcome them

No temptation has overtaken you except what is common to mankind. And God is faithful; he will not let you be tempted beyond what you can bear. But when you are tempted, he will also provide a way out so that you can endure it.

In the Greek, the understanding of trials and temptations can be understood to represent the bad circumstances of life that strengthen an individual.

In terms of scripture, no:

(Genesis 19:24) Then the LORD rained upon Sodom and upon Gomorrah brimstone and fire from the LORD out of heaven

I think it is pretty clear that scripturally speaking that is not a satanic action.

The believer would argue that if God is ordering something done, then it is (by definition) Good, and I don't see any scriptural reason to outsource it.

In terms of logic, no:

"Good" and "bad" are such absolutes, yet in many cases that which is bad for one person directly or indirectly benefits another (for example, an organ becoming available for transplant much to the benefit of a patient generally means somebody else had a really bad day). I don't suggest (although some will) that this is a deliberate act by any force or agency; simply: stuff happens. It isn't about you.