No. Yamgo never has access to your HBARs or your Private key. Yamgo can never take any HBARs from your account. Yamgo only has the ability to give you HBARs.
In order to create your Hedera Hashgraph account, you must provide Yamgo with a PUBLIC key. This is required in order to secure the account so that only the corresponding SECRET key can access it.
Regardless of whether you use the PUBLIC key provided by Yamgo or use a custom key generated elsewhere, this is the only information we use to create your account, and as such have no access to the HBARs or other tokens associated with the account.