I am struggling remembering when to use the above. Has anybody, worked out an easier way of remembering them? Plis
The first two come from cael - to have/receive.
The second two come from gwneud - to do.
Try this. There’s no N in cael, so nest ti and nes i have to be gwneud. Therefore the gest ti and ges i are cael!
If you’re talking about yourself, you say “I had/ I did”, and so you use the ones with just an ‘i’ - ges i and nes i.
If you want to say “You had / You did”, (lateral thinking here - ) U is next to T in the alphabet, so you use the ones with ‘ti’ - gest ti and nest ti.
There may be easier ways, but don’t worry - they will click into place with practice (rather than having to remember convoluted tips!) 
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