参观一个修道院

参观一个修道院
昨天是公休假日，Though 公休假日 is a correct expression in law, it sounds odd in colloquial language and in informal written style like this. I will recommend 昨天是休假日。

我们参观了一个修道院。它叫Montserrat。 我们和一些个朋友一起去。一些&一些个are both right, while the former is a more regular phrase.

我们的朋友也有一个女儿/小女孩子，她和我的女儿一样的岁同岁， 但是在不同的学校。（小女孩 don't refer especially to “daughter” in Chinese, but a little girl, not necessarily be "daughter".So if you want to express exactly as "Our friends have a daughter", it s better to use 女儿）

我们早上九点离开出发（or离开家）。天气很好， 不太热。我们坐火车，花了一个小时。Montserrat在山上。 这座 山很美丽。然后火车我们坐吊车上山。两个女孩子（deleted）很兴奋。我们在那里吃午饭。

然后吃我们在山上漫步（在山上走一点sounds odd）。 昨天是假日，所以有很多人。我们下午回家。两个女孩累极了。 

女孩子 is the expression used in last century or by classical writers. It won't be seen as often as "女孩" in modern Mandarin.

Visit to a monastery.
Yesterday was a public holiday. We visited a monastery. Ti is called Montserrat. We went with some friends. Our friends have a daughter the same age as our daughter, although she goes to a different school. We left home at 9am. The weather was good, not too hot. We went by train, it took an hour. Montserrat is in the mountains. They are beautiful mountains. After the train we took a cable car. The 2 girls were very excited. We ate lunch there. After lunch we walked a bit on the mountain. As yesterday was a holiday there were a lot of people. In the afternoon we came home. The girls were very tired.

参观一个修道院

参观一个修道院
昨天是公休日，我们参观了一个修道院。它叫Montserrat. 我和我一些朋友一起去。我的朋友也有一个女儿，她和我的女儿一样大， 但是读不同的学校。我们早上九点离开。天气很好， 不太热。我们坐火车，花一小时。然后我们坐观光车。Montserrat在山上。这山很美丽。两女孩子很兴奋。我们在那里吃午饭。 吃完饭，我们爬山。因为 昨天是假日，所以有很多人。我们下午回家。两女孩子累极了。
Visit to a monastery.
Yesterday was a public holiday. We visited a monastery. Ti is called Montserrat. We went with some friends. Our friends have a daughter the same age as our daughter, although she goes to a different school. We left home at 9am. The weather was good, not too hot. We went by train, it took an hour. Montserrat is in the mountains. They are beautiful mountains. After the train we took a cable car. The 2 girls were very excited. We ate lunch there. After lunch we walked a bit on the mountain. As yesterday was a holiday there were a lot of people. In the afternoon we came home. The girls were very tired.

I will write it this way:

参观修道院 ("一个"can be omitted for simplicity in a title)

昨天是公共假期，我和几个朋友去参观一个叫XX的修道院。其中一个朋友也有个女儿，和我女儿同岁，但上不同的学校。我们早上九点出发，天气很好，不太热。我们坐了一小时的火车，然后坐缆车到山上的XX。两个孩子很兴奋。我们在那里吃了午饭，然后在山里走了一会儿。因为是假日，游人特别多。我们下午才回家，孩子们累极了。

I also rearrange the order of sentences a bit for a better flow.

The monastery is amazing!

参观一个修道院

参观一个修道院
昨天是公休假日，我们参观一个修道院。它叫Montserrat. 我们和些个一些（一些=some）朋友一起去。我们的朋友也有一个小女孩子女儿（both are correct, but “小女孩子”=little girl in Chinese while "女儿"=daughter），她和我的女儿一样的岁数（seperately, "岁"=age and "数"=number, but "岁数" is more common and natural）， 但是在不同的学校。我们早上九点离开。天气很好， 不太热。我们坐火车，花一小时。Montserrat在上山山上（“上山”=climb the moutain, "山上"=in the mountain）。这山很美丽。然后火车我们坐上山吊车。两女孩子很兴奋。我们那里吃午饭。 然后吃吃完午饭（=after eating lunch）我们往上山走一点儿。 因为（=As）昨天是(=was)假日，所以有很多人。我们下午回家。两女孩子累极了。

Tip: In Chinese, not like English, "因为"(=because/as/since) can be used with "所以"(=so).

参观一个修道院

参观一个修道院
昨天是公休假，我们参观一个叫montserrat的修道院。 我们是和一个朋友一起去的。我们的朋友也有一个女儿，她的女儿和我的女儿年龄一样大， 但是在不同的学校学习。我们早上九点出发。天气晴朗，我们坐火车，花费一小时到达了Montserrat所在的山的山脚下，然后我们坐上缆车去山上了。两个女孩子很兴奋。我们在那里吃午饭。 之后我们往山上走了一下。 昨天假日所以有很多人。我们下午便回家了。两女孩子累极了。
Visit to a monastery.
Yesterday was a public holiday. We visited a monastery. Ti is called Montserrat. We went with some friends. Our friends have a daughter the same age as our daughter, although she goes to a different school. We left home at 9am. The weather was good, not too hot. We went by train, it took an hour. Montserrat is in the mountains. They are beautiful mountains. After the train we took a cable car. The 2 girls were very excited. We ate lunch there. After lunch we walked a bit on the mountain. As yesterday was a holiday there were a lot of people. In the afternoon we came home. The girls were very tired.