As you can see, except for 2 functions marked as 'view', all of them are not view functions.
So you should call them as staticCall to get the result returned.
logYield data on PoolData struct refers to LP's APR of growing due to accumulated swap fees. You could calculate the APR like this :
APR(%) = 2^(logYield * 86400 * 365 / 1e18) * 100
Functions you could use to get details about Gauge and Pools