and buy bitcoin for the rest (30-40 percent) but since btc price is highly increased you think i should just keep
doing the same or i should buy USDT instead with that 30-40 percent meant for bitcoin and store it in a safe wallet
like trezor till btc price drop or till we see a new bear market then buy btc with that saved USDT
I would split these 30-40% into 2 halves.
I would buy bitcoin for the 1st half, now, despite the high current price. And I would exchange the 2nd half for cash (but not in the form of local currency) and would wait for a strong drop in value or a bear market. During which, in turn, I would start buying up bitcoin.
Why wouldn't I keep it in USDT? Because it is unknown what fate awaits this coin tomorrow, and quite a lot of time may pass before bitcoin falls. Dollar, in turn, remain a reserve currency and this will not be "cancelled" right tomorrow.
The advantage of this method may be that you will have cash on hand (in case of emergency) and will not have to exchange bitcoin at an unfavorable rate that may arise.