Read some textbooks first. For institutions, you can read the book "Lifting Machinery". The book written by Yang of Dalian University of Technology is the most classic, and that written by Ni Qingxing of Shanghai Jiaotong University is also good, which is more concise than Yang. These two books are hard to find in the market now. You can read Lifting and Transportation Machinery by Metallurgical Press or Lifting and Transportation Machinery by Zhengzhou University Press. Structurally, there are three classic works. The first one is Xu's metal structure, which is more comprehensive, but unfortunately it is not easy to buy. His son Xu Gening's Metal Structure of Mechanical Equipment is based on this and can be read. There is also the "Metal Structure for Lifting and Transportation" published by Wang of Southwest Jiaotong University in 2002, which is more practical and general. There is also "Metal Structure of Hoisting Machinery" by Chen of Shanghai Maritime University, which is currently being revised by his disciple Professor Dong Dashan. It is estimated that it will be published soon, and it is also a classic book.
After reading the books on mechanism and structure, you can learn GB/T38 1 1-2008 Code for Design of Cranes and GB6067 Safety Regulations for Cranes. You should be familiar with the structure of the crane, look at the physical objects and old drawings, and learn to draw pictures, and you will learn it slowly.