Timestamps of each trial is in the pinned comment below. Use it to skip to the respective Trial.
I also created a discord channel to discuss anything related to Fire emblem heroes be it unit building for arena, grand hero battle, or quest. I will answer questions there whenever I am free. Feel free to join if you have an account. (￣▽￣)ノ
https://discord.gg/7aWzaaa
Here are some old videos if you need help in leveling or farming SP.
SP Farming Guide : https://youtu.be/n_PINy_S7Ec
Power Leveling Guide 1-40 : https://youtu.be/VoafKXPROqU