how do i make bigger models because turns out the size limit is only 19 cubes

[weak hinge]

You can try using multi-part models

[gaunt nebula]

turns out the size limit is only 19 cubes
where did you get "19" from 🤔 ?

!faq java-sizelimit

[quaint burrow]

Java block and item models can only contain elements between -16 and 32 in the edit mode (which is the equivalent of 3 blocks ingame). They are limited to this size by the format, not just by Blockbench.

Item models can be displayed larger ingame by going to the display mode (top right) and using the scale slider to resize the model.
Maximum size in blocks for the different slots (when the model is 3x3x3 blocks big in edit mode and scale is set to 4):

Slot | Size | Base Size Multiplier
Head | 7.5 | 0.625
Hand | 12.0 | 1.000
Item frame | 6.0 | 0.500
(Formula = 3 x 4 x base_size_multiplier)

Keep in mind that a model stops rendering with the entity holding/wearing it. An entity stops rendering once its hitbox is not in your point of view anymore.

[gaunt nebula]

I should probably add a mention of item display entities to this at some point.

[quaint burrow]

(Result for "precise-movement")
To move/scale cubes in smaller increments than 1 you can hold the following key combinations:
-Shift: 0.25
-Ctrl: 0.1
-Ctrl+Shift: 0.025
If those default values are not to your liking you can change these incrementsin File > Preferences > Settings > Snapping

PS: If you want to allign 2 elements we suggest using the vertex snapping tool instead (see !faq vertex-snapping for more info)
Disclaimer: The modded entity format does NOT allow decimal cube sizes and neither does the Optifine Entity format if box-uv is enabled!

[gaunt nebula]

still same restrictions
and still not sure where the "19" comes from

then that just means your cube is at position 13 on that axis

hence why it stopped at 19 (cause 13+19 = 32)

yes

that means your cube is at y position 13