raisyuu ha siken ga aru node, konya ha geemu bakari site iru wake ni ha ikimasen.

This is a very common pattern in Japanese.

• 来週は sets the topic/time frame: as for next week
• 試験がある says what exists in that time frame: there is an exam / I have an exam
• 今夜は sets a new topic/time frame: as for tonight

So the sentence is structured like this:

• As for next week, there is an exam, so...
• As for tonight, I can’t...

The two は markers also create a natural contrast between next week and tonight.

Literally, 試験がある means there is an exam.

But in natural English, it often means:

• I have an exam
• There’s an exam scheduled
• An exam is coming up

Japanese often uses ある with events, appointments, meetings, tests, and so on.

Examples:

• 会議がある = I have a meeting
• 授業がある = I have class
• 試験がある = I have an exam

So even though English uses have, Japanese often uses exist / occur language instead.

ので means because or since.

In this sentence:

• 来週は試験があるので = because I have an exam next week

Compared with から, ので usually sounds:

• a little softer
• a little more explanatory
• a little more objective

So:

• 試験があるから can sound more direct
• 試験があるので sounds a bit gentler and more matter-of-fact

Both are possible, but ので fits well when giving a reason in a calm, explanatory way.

Because ばかり is attached directly to the noun.

So:

• ゲームばかりしている = to be doing nothing but playing games

Here, ばかり is focusing on ゲーム and means nothing but / only.

You can think of it like this:

• ゲームをしている = be playing games
• ゲームばかりしている = be doing nothing but playing games

When ばかり is used this way, the usual object marker を is often omitted.

ばかり means only, nothing but, or just.

In this sentence:

• ゲームばかりしている = doing nothing but playing games

It often carries a nuance that the amount is excessive or not ideal.

So this does not just mean a neutral only. It suggests something like:

• playing games and not doing other things you should do
• spending all your time on games

That nuance fits the rest of the sentence, because the speaker has an exam next week.

Because している emphasizes an ongoing or continuing activity.

• ゲームばかりする = to play nothing but games, in general / habitually
• ゲームばかりしている = to be spending one’s time doing nothing but playing games

In this sentence, the speaker is talking about tonight, so している fits the idea of a continuing situation:

• I can’t spend tonight just playing games
• I can’t keep doing nothing but playing games tonight

So している makes the image more immediate and concrete.

This is an important grammar pattern.

V-る / V-ている / V-ない + わけにはいかない means:

• cannot do such a thing
• cannot allow oneself to do that
• cannot very well do that
• can’t afford to do that

It does not usually mean physical inability.

Instead, it means the speaker feels they should not do it because of:

• duty
• common sense
• responsibility
• social reasons
• practical circumstances

So here:

• ゲームばかりしているわけにはいきません

means something like:

• I can’t just spend my time playing games
• I can’t afford to do nothing but play games
• It wouldn’t be right for me to just keep playing games

because there is an exam next week.

In わけにはいかない, the は is part of the set expression.

Breaking it down loosely:

• わけ = reason / circumstance / situation
• に = in / as
• は = contrast or emphasis
• いかない = won’t go, won’t do

The whole phrase functions idiomatically, so it is best learned as one unit:

• わけにはいかない = cannot very well do
• わけにはいきません = polite version

The は adds a contrastive/emphatic feeling, something like:

• as for doing that, it just won’t do

But in practice, you should memorize the whole pattern rather than try to translate each piece literally every time.

Because this expression is based on いく, not いけない.

The dictionary form of the pattern is:

• わけにはいかない

Its polite negative form is:

• わけにはいきません

This is different from the separate pattern:

• てはいけない = must not / may not

So:

• してはいけない = you must not do it
• しているわけにはいかない = you can’t afford to be doing that / you cannot very well keep doing that

They may feel similar in English sometimes, but they are different grammar patterns.

No, not necessarily.

The nuance is usually softer and more realistic than an absolute prohibition.

It means something like:

• I shouldn’t spend tonight just playing games
• I can’t afford to do nothing but play games tonight
• Given that I have an exam next week, I can’t justify that

So the speaker is expressing self-restraint or obligation, not usually a strict external rule.

It leaves open the possibility that they might play a little, but they cannot spend the whole evening doing only that.

Using は after 今夜 makes tonight the topic and adds a slight contrastive nuance.

It can feel like:

• as for tonight
• at least tonight
• tonight, given the situation...

That works well here because the sentence is contrasting the current situation with what would normally be okay.

So 今夜は suggests something like:

• Tonight, I can’t just play games
• maybe on another night it would be fine, but tonight is different because of the exam next week

This kind of subtle contrast is one of the common jobs of は.