This school year we have visited many interesting places. - верно.
We have gone to the Excursion of the museum this month. - после глагола go только to
It was interesting because there were a lot of beautiful pictures in the museum which we liked very much. - здесь не скажешь в Present Prefect
Also the museum guide has told us very interesting history about these famous pictures. - так тоже не говорят, но с точки зрения грамматики предложение построено верно.
We were happy because we have already gone to this excursion and have learnt a lot. - то же как и в предыдущем предложении, лучше было бы просто в Past, но раз задание только в Present Perfect, пусть будет так.
Best of all I liked waching the pictures which I have never seen before. - Больше всего мне понравилось рассматривать картины, которые я никогда не видела раньше.
