Israel is buying weapons from the US this year. (An unusual and temporary activity that’s happening only this year – this is also implied by the grammatical structure itself, irrespective of the time expression. )

Israel buys weapons from the US. (Fact – this information is true in general, it was true yesterday, it is true today and as far as we know will be true tomorrow. ) 

They’re going swimming this week. (An unusual and temporary activity that’s happening only this week – this is also implied by the grammatical structure itself, irrespective of the time expression.) 

They go swimming every Friday. (Habit – this activity happens regularly every Friday. This was true yesterday, it is true today and as far as we know will be true tomorrow. ) 

He’s working as a substitute Hebrew teacher this week. (An unusual activity that’s happening only this week – this is also implied by the grammatical structure itself, irrespective of the time expression. )  

He works as an English teacher. (A permanent situation – this is what he does on a daily basis, consistently. this was true yesterday, it is true today and as far as we know will be true tomorrow.)

He’s talking on the phone, reading the news and having breakfast at the same time. (Simultaneous actions – these actions do not happen regularly or daily, rather actions happening in a specific time frame.)

He gets up at 8:00, washes his face, gets dressed and goes to work. ( Chronological actions in the present – this is performed regularly on a daily basis.)

I’m thinking of buying a new car. (A process of thinking – this is an activity happening in a specific time frame, something I’m considering recently.) 

I think you are right. (Opinion – the word “think” in the sentence does not represent a process of thinking but rather a general opinion about a certain subject.)

You must come to the party, I’m insisting on it. (A dynamic process – in which the other person insists again and again on something. The -ing is used to reflect this process of insistence.) 

I insist we go out tonight. (Doing things by saying them – the speaker presents their (general) position about something.)

I’m arriving to Toronto tomorrow. (Personal schedule – this schedule is true only for me, it is a specific and personal schedule.) 

The bus arrives in 5 minutes. (Impersonal schedules – this schedule applies to everyone standing at the bus stop, hence it is not personal.

They’re staying here for a few days. (A Temporary situation – this is not permanent or factual.)

They are here. (A defining sentence in the present – there are no set time constraints for their stay. This statement provides very general information. )