What features (lesson plans, dictionary, SRS, etc.) are you looking for in the app?  If you're a complete beginner there are apps like Hello Chinese and Chinese Skill which are popular.  They will teach you pronunciation with pinyin as well.  Make sure you get corrected by a native speaker though :)

If you just want a dictionary, I like Pleco.

Most good apps have the option to switch to traditional characters, but default to simplified.  I've only seen a couple of apps that are strictly simplified, but they typically state they have plans to support traditional in the future.

I'm neither a grammar expert nor a native Mandarin speaker, but I think you're confusing the object "學校" with the where component. The where often starts with "在".

The closest thing I found to help you out with this is in this article: https://www.italki.com/article/582/The-Golden-Rules-Of-Chinese-Word-Order

Anyway, perhaps the following modification will help you out: 我明天在北京會去學校。

If I'm wrong, hopefully this will at least give a native speaker a better understanding of your question.

Sorry for the 繁體字. It's too early and I'm too lazy to figure out how to switch to 簡體字...

Word practice 10-23

While technically correct, it would sound more natural to say, "Please note the safety notice on the wall."  It sounds awkward to say notice twice.

2 Take no notice of what he says.
3 She was transferred without notice.

Wish
1 I can give three wishes to your.
2 I just have one wish.
3 I wish I was taller.

Step
1 I heard steps outside.
2 He took a step towards that girl.
3 He is walking up the steps.

Practical
1 My boseboss(?) was always so practical.

Bose isn't a word.  I'm assuming you mean boss.

2 He givegave me some practical advice.
3 This robot is so practical; it can even cook.

Corner
1 I saw a dog in your house's corner.
2 I hit my knee on the corner of the table.
3 The girl sat in the corner of the room.

Wonder
1 I wonder who she is?
2 I wonder if you can help me?
3 Thew woman wonders if she carries a boy ofor a girl.

Alive
1 I was glad to hear you're alive and well.
2 Is your cat alive?
3 "I'am alive!" said the monster.

Satisfaction
1 She is not satisfaction forsatisfied with this service.
2 She felt a small glow of satisfaction.
3 They had satisfaction in their life.

Monitor
1 He was elected monitor.
2 The teacher is talking to the monitor.
3 He is the moniteor in our class.

I think it would be better to say either, "He is a monitor in our class," or "He is the monitor of our class," depending on how many are allowed.

Queue
1 I had to join a queue for the toilets.
2 There is a long queue of hundereds of people.
3 How long were you in the queue?

This is a good idea.  I wish I had enough discipline to do these exercises.  Good luck with your studies!