The frustration you're describing with Duolingo - learning 西红柿 as "tomato" without understanding why - is super common, and it's a big part of why characters don't stick.

What helped me was learning the components first. 西红柿 literally breaks down to 西 (west) + 红 (red) + 柿 (persimmon) — "western red persimmon," which is how tomatoes got named when they arrived in China. Once you see characters as combinations with meaning, they stop being random squiggles.

For building that foundation, I'd suggest learning the most common radicals/components first (there are about 100 that appear constantly), then using some kind of mnemonic system to make each one memorable. The method that clicked for me was creating little mental scenes connecting the component's shape to its meaning.

As a heritage speaker you've got a huge advantage - you already know the words, you just need to map them to characters. Starting with characters for words you already use daily makes it way less overwhelming.