What is the possible for low Payload and high DL PRB utilization?

Sinr is bad.

SINR below 0
RSSI is above -25 dBm
RSRP is abive -60 dBm
RSRQ is above -16

And detected neighbours RSRP are below -70 dBm.

You should reduce footprint of those RSRP near of -70 dBm.

Check the number of active users.

The same happened with me as well.

The traffic was low but PRB utilization was max but the number of active users were very high causing high utilization.

What should I do if the number of active users are high causing low DL Throughput?

Restrict the footprint of this cell if itā€™s overshooting.

Lower power, downtilts, deboost etc.

TA is normal and not overshooting.

Still you may need to try to shift users to NBR cells by applying some offsets and shrinking its coverage.

May be cqi is not good in that cell and bler.

You said that RRC connected user during BH is 100, right?

Yes, correct.

I think 100 user is not really high for 300 lic and 20 MHz.

Apparently you should check radio condition.

UL Throughput is very good, more than 60 Mbps.

But DL Throughput is less than 20 Mbps.

Check DL bler, SINRā€¦

SINR is bad (below 0).

Rssi is above -25 dBm.
Rsrp is above -60 dBm.
Rsrq is above -16.

And detected neighbours RSRP are below -70 dBm.

You shoud reduce footprint of those RSRP near of -70 dBm.

RSRP of NBR pleaseā€¦

RSRQ is very poor.