Put the verbs in brackets into the present simple, present continuous, present perfect or present perfect continuous.
Hi! How are you? ..(not\hear) from you for a while. I... (guess) toy. 3)...(study)for your exams for the last few weeks like me. I...(sit) most of them. I...(sit) the last one this Friday. I...(think) that I...(do) quite well. My friends and I (throw) a big party to celebrate this weekend. We ...(already \ hire) the village hall. ..(you \ make) any plans for Saturday night yet? If not, why don't you come? It... (start) at 8 p.m. and you can stay at my house. Paula and Eve... (stay) too so it'll be fun. Let me know. Write back soon. 
Love,
Lisa

Hi! How are you? I HAVEN’T HEARD from you for a while. I... GUESS  YOU 3 HAVE BEEN STUDYING for your exams for the last few weeks like me. I HAVE SAT  most of them. I AM SITTING  the last one this Friday. I THINK  that I AM DOING?/I have been doing? (здесь не уверена) quite well. My friends and I ARE THROWING a big party to celebrate this weekend. We . HAVE ALREADY HIRED the village hall. HAVE YOU MADE any plans for Saturday night yet? If not, why don't you come? It STARTS at 8 p.m. and you can stay at my house. Paula and Eve ARE STAYING too so it'll be fun. Let me know. Write back soon.

I think, I AM DOING :)