FPGA design has spread into many levels recently (i just add some reference links, you can find more):
Low level: Hardware language design (RTL/logic design w/ VHDL and Verilog) and HW basic components (Luts, core, bus, peripherals)
(https://www.mhprofessional.com/9781259837906-usa-digital-system-design-with-fpga-implementation-using-verilog-and-vhdl-group,
https://www.coursera.org/learn/intro-fpga-design-embedded-systems, ....)
High level: High-level language design (C/C++) w/ extra components (FPGA + SoC + external RAM...) and let the support tool to compile
(High-Level Synthesis Blue Book, https://www.youtube.com/watch?v=kgae3Wzqngs&list=PLa8My9ttt2c-hDUG7Q4mNR18r-5Gh0vDO ...)
Applicant level: Today, you even can work with FPGA through Python API and build a fantastic app with machine learning
(https://github.com/Xilinx/Edge-AI-Platform-Tutorials...)
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I think you can start with a small module (eg: a multiplier) and learn the HW architecture, logic design, then move forward
I may lack some info. but basically you can search more when you start to dig in :)
Good luck